In my solution, I have a navigation bar set to hex color #ffcc00 (dark yellow) with buttons set as part of a method to the same color with text in #336699 (dark blue). Each time a button is pressed it changes the color of that button to #336699 (dark blue) with white text and sets all other buttons to the original color. In Developer, this works perfectly however when opening the solution in Client using the Mac OSX LAF, the buttons appear in white and when pressed the text changes to white and thus is invisible. Additional information that might help is that the navigation panel does display correctly in #ffcc00 (dark yellow) and other elements in dark blue also appear as white.
Switching the LAF to Kunstorff resolves the problem.
Using latest version of Servoy R2.1.1, developing on a WinXP laptop.