With anything other than white, the tCurvyCombo Drop Down style is drawn in an unsatisfactory way - and it is even worse as a Drop Down List. See this demo:
With the cursor rollover Hot Colours there are also some unusual issues:
The colouring of the standard VCL control itself is not entirely satisfactory as a Drop Down but it would be nice if there was some consistency and the tCurvyCombo Drop Down List can certainly be improved by copying the coloring of the VCL (ie ignoring the color property altogether).