I like to make bitmap transparent particular color and transculent (all colors in bitmap),

For this CXFORMWITHALPHA record added to the object.

1) For translucent, I gave mult r = 255, g = 255, b = 255 and a = 0 value. This made translucent (full transparent) . Is this correct procedure or not?

2) If bitmap contains multiple colors then how we need to give the record to make bitmap only specified color transparent and other color should not change? Is it possible? if it is possible please inform me the procedure.