using VS 2003 and VAX 1418 when i hover the mouse over a function call or definition in C++ code the tooltip that shows me the function prototype is coloured by VAX.
if you provide some more details, and perhaps a screen shot of the effect in action perhaps i can help.
the language and IDE would be a good start. plus have you done anything strange to your colour scheme?
Color in tooltips display wrongly! one example: the source code: class CEvaluateDlg : public CDialog in tooltip: class CEvaluateDlg : public CDialog {...}