I'm using Linux Mint 17KDE with a minimalistic qtcurve theme. There seems to be settings for everything except the color, or shade, of the foreground button graphics. These are the small icons that exist on the buttons. In the preview window for qtcurve they can be found next to the text labels for Open, Save, Cut, etc. When the button background is made light colored they automatically change to black. But when you want a dark theme you might expect them to change to white, but instead they automatically change to dark grey, which does not work.
Could someone please point to the settings from which this automatic switch is drawing from so I can get the contrast I need for my setup? I have three PCs that I would love to implement this on.

Thanks

I have since switched to Debian 8 to try to get away from some of the extras that have been packaged in with Mint. It appears the switch goes to graphical icon sets, one for dark, one for light. I don't know for sure. They don't seem to part of a user changeable theme but I could be wrong about that as well. The icons that come with debian work much better.

I'm pretty sure the icons you are talking about are provided by the icon theme. Icon themes often come in light and dark varieties, which usually applies to the icons used on the various ui elements (buttons, menus, etc.) when using light and dark color schemes.
I don't know what, if any, auto-detection is done on the color scheme before deciding whether to use the light or dark variants. I would assume that it does none since the dividing line between when one variant or another is preferred depends on the icon theme in question.