The Tk command tk_bisque, documented in 
http://www.purl.org/tcl/home/man/tcl8.4/TkCmd/palette.htm
is implemented in the Tk library file palette.tcl .

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[palette] - [tk_setPalette] -
[Tk syntax help] - [Arts and crafts of Tcl-Tk programming] - [Category Command] from [Tk]