vhdl-special-syntax-alist

vhdl-special-syntax-alist is a variable defined in `vhdl-mode.el'.
Its value is

(("generic/constant" "\\<\\w+_[cg]\\>" "Gold3" "BurlyWood1" nil)
 ("type" "\\<\\w+_t\\>" "ForestGreen" "PaleGreen" nil)
 ("variable" "\\<\\w+_v\\>" "Grey50" "Grey80" nil))

Documentation:
List of special syntax to be highlighted.
If option `vhdl-highlight-special-words' is non-nil, words with the specified
syntax (as regular expression) are highlighted in the corresponding color.

Name : string of words and spaces
Regexp : regular expression describing word syntax
(e.g. "\<\w+_c\>" matches word with suffix "_c")
expression must start with "\<" and end with "\>"
if only whole words should be matched (no substrings)
Color (light): foreground color for light background
(matching color examples: Gold3, Grey50, LimeGreen, Tomato,
LightSeaGreen, DodgerBlue, Gold, PaleVioletRed)
Color (dark) : foreground color for dark background
(matching color examples: BurlyWood1, Grey80, Green, Coral,
AquaMarine2, LightSkyBlue1, Yellow, PaleVioletRed1)
In comments : If non-nil, words are also highlighted inside comments

Can be used for visual support of naming conventions, such as highlighting
different kinds of signals (e.g. "Clk50", "Rst_n") or objects (e.g.
"Signal_s", "Variable_v", "Constant_c") by distinguishing them using
common substrings or name suffices.
For each entry, a new face is generated with the specified colors and name
"vhdl-font-lock-" + name + "-face".

NOTE: Activate a changed regexp in a VHDL buffer by re-fontifying it (menu
entry "Fontify Buffer"). All other changes require restarting Emacs.

You can customize this variable.