Check which theme you are using from the .gtkrc file in your home directory. if it is using a different theme then you'll probably see a line like
Code:
include "usr/share/themes/<the theme you choose>/gtk/gtkrc"
Go to that gtkrc file and look for the following code
Code:
style "default" {
text[ACTIVE] = "#ffffff"
text[INSENSITIVE] = "#000000"
text[NORMAL] = "#000000"
text[PRELIGHT] = "#000000"
text[SELECTED] = "#ffffff"
Change the value for Active text. I think that should do it.