There might be a .gtkrc-2.0 file in your home directory--or there may not. I don't recall having one in VL6 Standard until I put this one in there, but I do see one in VL6 Light, which I'm using right now on my laptop. However, its contents are nothing like the one I attached, which I guess is specific for XFce.
If you already have a .gtkrc-2.0 file in your home directory, rename it to something like .gtkrc-2.0_old and then do what I said. Just download the attachment in my earlier message, remove the .txt extension so that the file is named .gtkrc-2.0, and put it in your home directory. It doesn't go in a subdirectory of your home directory; it goes in the section *after* the directories where there are a bunch of files that begin with dots (they are hidden files--be sure your file manager is set to show hidden files).
Read my earlier message again so you know how to change the file if you want white text or black text for icon names.
If this is still not clear, let me know and I'll try again. By renaming an existing .grkrc-2.0 rather than overwriting it, you can easily recover if you're not happy with the results of trying the file attachments. You would just delete .gtkrc-2.0 and rename .gtkrc-2.0_old to .gtkrc-2.0 and you'd be back where you were before, but you have to log out of XFce and log back in for the changes to take effect.