Preserving specific colors

This question might be a little difficult to explain. Let me see...

I'm developing a program that, among other things, must be able to
show a series of pictures one at a time. No problem in that.

The trick comes here:

1) The program MUST run in 256 colors

2) Every picture use exactly 220 colors (indexed as the first 220
colors in the bitmap-file's color-table

3) The remaining 36 colors (the last 36 in the color table) are used
by the program as "standard" colors (I want to override Windows'
standard colors)

4) It is *VERY* important that, when a new image is loaded, it does
not overwrite my 36 standard colors - they MUST be preserved.

Example:

*******************************
* Image (220 colors)          *
* with changing pictures      *
*                             *
*******************************
* Panel with 36 static colors *
*******************************

How is that done?

Do I need to inherit TBitmap and override the Load-methods to make
sure where the colors are put?

-- Carsten