vhdl-highlight-special-words

vhdl-highlight-special-words is a variable defined in `vhdl-mode.el'.
Its value is

nil

Documentation:
Non-nil means highlight words with special syntax.
The words with syntax and color specified in option `vhdl-special-syntax-alist'
are highlighted accordingly.
Can be used for visual support of naming conventions.

NOTE: Activate the new setting in a VHDL buffer by re-fontifying it (menu
entry "Fontify Buffer").

You can customize this variable.