This command (possibly) changes the two colors fg and bg to the foreground and background color of the ⟨beamer-color name⟩. If the beamer-color does not specify a foreground, fg is left unchanged; if does not specify a background, bg is left unchanged.

You will often wish to directly use the color fg or bg after using this command. For this common situation, the optional argument ⟨fg or bg⟩ is useful, which may be either fg or bg. Giving this option will cause the foreground fg or the background bg to be immediately installed after they have been setup. Thus, the following command

\usebeamercolor[fg]{normal text}

is a shortcut for

\usebeamercolor{normal text}
\color{fg}

If you use the starred version of this command, the beamer-color normal text is used before the command is invoked. This ensures that, barring evil trickery, the colors fg and bg will be setup independently of whatever colors happened to be in use when the command is invoked.

This command has special side-effects. First, the (normal) color parent.bg is set to the value of bg prior to this call. Thus you can access the color that was in use prior to the call of this command via the color parent.bg.

Second, the special color ⟨beamer-color name⟩.fg is globally set to the same value as fg and ⟨beamer-color name⟩.bg is globally set to the value of bg. This allows you to access the foreground or background of a certain ⟨beamer-color name⟩ after another beamer-color has been used. However, referring to these special global colors should be kept to the unavoidable minimum and should be done as locally as possible since a change of the beamer-color will not reflect in a change of the colors ⟨beamer-color name⟩.fg and ⟨beamer-color name⟩.bg until the next invocation of \usebeamercolor. Also, if the ⟨beamer-color name⟩ does not specify a foreground or a background color, then the values of the special colors are whatever happened to be the foreground or background at the time of the last invocation of \usebeamercolor.

So, try not to get into the habit of writing \color{structure.fg} all the time, at least not without a \usebeamercolor{structure} close by.

Example:

 This text is {\usebeamercolor[fg]{alerted text} alerted}. The
 following box uses the fore- and background of frametitles:
 {
   \usebeamercolor[fg]{frametitle}
   \colorbox{bg}{Frame Title}
 }

This command has no effect in article mode.

This command can be used to check whether the foreground or background of some ⟨beamer-color name⟩ is non-empty. If the foreground or background of ⟨beamer-color name⟩ is defined, ⟨if defined⟩ will be executed, otherwise the ⟨if undefined⟩ code.

Example:

\ifbeamercolorempty[bg]{frametitle}
{ % ``Transparent background''
  \usebeamercolor[fg]{frametitle}
  \insertframetitle
}
{ % Opaque background
  \usebeamercolor[fg]{frametitle}
  \colorbox{bg}{\insertframetitle}
}

Sets or changes a beamer-color. The ⟨beamer-color name⟩ should be a reasonably simple text (do not try too much trickery and avoid punctuation symbols), but it may contain spaces. Thus, normal text is a valid ⟨beamer-color name⟩ and so is My Color Number 2.

In the most simple case, you just specify a foreground by giving the fg= option and, possibly, also a background using the bg= option.

Example: \setbeamercolor{normal text}{fg=black,bg=mylightgrey}

Example: \setbeamercolor{alerted text}{fg=red!80!black}

The effect of this command is accumulative, thus the following two commands

\setbeamercolor{section in toc}{fg=blue}
\setbeamercolor{section in toc}{bg=white}

have the same effect as

\setbeamercolor{section in toc}{fg=blue,bg=white}

Naturally, a second call with the same kind of ⟨option⟩ set to a different value overrides a previous call.

The starred version first resets everything, thereby “switching off” the accumulative effect. Use this starred version to completely reset the definition of some beamer-color.

The following ⟨options⟩ may be given:

• • fg=⟨color⟩ sets the foreground color of ⟨beamer-color name⟩ to the given (normal) ⟨color⟩. The ⟨color⟩ may also be a color expression like red!50!black, see the manual of the xcolor package. If ⟨color⟩ is empty, the ⟨beamer-color name⟩ “has no special foreground” and when the color is used, the foreground currently in force should not be changed.

  Specifying a foreground this way will override any inherited foreground color.

• • bg=⟨color⟩ does the same as the fg option, but for the background.

• • parent=⟨parent beamer-color(s)⟩ specifies that ⟨beamer-color name⟩ should inherit from the specified ⟨parent beamer-color(s)⟩. Any foreground and/or background color set by the parents will also be used when ⟨beamer-color name⟩ is used. If multiple parents specify a foreground, the last one “wins”; and likewise for the backgrounds.

  Example:

  \setbeamercolor{father}{fg=red}
  \setbeamercolor{mother}{bg=green}
  \setbeamercolor{child}{parent={father,mother}}
  \begin{beamercolorbox}{child}
    Terrible red on green text.
  \end{beamercolorbox}
  
  \setbeamercolor{father}{fg=blue}
  \begin{beamercolorbox}{child}
    Now terrible blue on green text, since parent was changed.
  \end{beamercolorbox}
  

  Note that a change of the foreground or background of a parent changes the corresponding foreground or background of the child (unless it is overruled).

  A beamer-color can not only have parents, but also grandparents and so on.

• • use=⟨another beamer-color⟩ is used to make sure that another beamer-color is setup correctly before the foreground or background color specification are evaluated.

  Suppose you wish the foreground of items to be a mixture of 50% of the foreground of structural elements and 50% of the normal foreground color. You could try

  \setbeamercolor{item}{fg=structure.fg!50!normal text.fg}
  

  However, this will not necessarily give the desired result: If the beamer-color structure changes, the (normal) color structure.fg is not immediately updated. In order to ensure that the normal color structure.fg is correct, use the following:

  \setbeamercolor{item}{use={structure,normal text},fg=structure.fg!50!normal text.fg}
  

  This will guarantee that the colors structure.fg and normal text.fg are setup correctly when the foreground of item is computed.

  To show the difference, consider the following example:

  \setbeamercolor{grandfather}{fg=red}
  \setbeamercolor{grandmother}{bg=white}
  \setbeamercolor{father}{parent={grandfather,grandmother}}
  \setbeamercolor{mother}{fg=black}
  {
    \usebeamercolor{father}\usebeamercolor{mother}
    %% Defines father.fg and mother.fg globally
  }
  \setbeamercolor{my color A}{fg=father.fg!50!mother.fg}
  \setbeamercolor{my color B}{use={father,mother},fg=father.fg!50!mother.fg}
  
  {\usebeamercolor[fg]{my color A} dark red text}
  {\usebeamercolor[fg]{my color B} also dark red text}
  
  \setbeamercolor{grandfather}{fg=green}
  
  {\usebeamercolor[fg]{my color A} still dark red text}
  {\usebeamercolor[fg]{my color B} now dark green text}
  

This command offers several different options, the most important of which is transparent. All options are internally mapped to the two options still covered and again covered.

In detail, the following ⟨options⟩ may be given:

• • invisible is the default and causes covered text to “completely disappear”.

• • transparent=⟨opaqueness⟩ causes covered text to be typeset in a “transparent” way. By default, this means that 85% of the background color is mixed into all colors or that the ⟨opaqueness⟩ of the text is 15%. You can specify a different ⟨percentage⟩, where 0 means “totally transparent” and 100 means “totally opaque.”

  Unfortunately, this value is kind of “specific” to every projector. What looks good on your screen need not look good during a presentation.

• • dynamic Makes all covered text quite transparent, but in a dynamic way. The longer it will take till the text is uncovered, the stronger the transparency.

• • highly dynamic Has the same effect as dynamic, but the effect is stronger.

• • still covered=⟨not yet list⟩ specifies how to render covered items that have not yet been uncovered. The ⟨not yet list⟩ should be a list of \opaqueness commands, see the description of that command, below.

  Example:

  \setbeamercovered{%
   still covered={\opaqueness<1>{15}\opaqueness<2>{10}\opaqueness<3>{5}\opaqueness<4->{2}},
   again covered={\opaqueness<1->{15}}}
  

• • again covered=⟨once more list⟩ specifies how to render covered items that have once more been covered, that is, that had been shown before but are now covered again.

The ⟨overlay specification⟩ specifies on which slides covered text should have which ⟨percentage of opaqueness⟩. Unlike other overlay specifications, this ⟨overlay specification⟩ is a “relative” overlay specification. For example, the specification “3” here means “things that will be uncovered three slides ahead,” respectively “things that have once more been covered for three slides.” More precisely, if an item is uncovered for more than one slide and then covered once more, only the “first moment of uncovering” is used for the calculation of how long the item has been covered once more.

An opaqueness of 100 is fully opaque and 0 is fully transparent. Currently, since real transparency is not yet implemented, this command causes all colors to get a mixing of ⟨percentage of opaqueness⟩ of the current bg. At some future point this command might result in real transparency.

The alternate pgf extension used inside an opaque area is ⟨percentage of opaqueness⟩opaque. In case of nested calls, only the innermost opaqueness specification is used.

Example:

\setbeamercovered{still covered={\opaqueness<1->{15}},again covered={\opaqueness<1->{15}}}
\pgfdeclareimage{book}{book}
\pgfdeclareimage{book.!15opaque}{filenameforbooknearlytransparent}

Makes everything that is uncovered in two slides only 15 percent opaque.