TBitmap of popup menu has different background on different PC

Hello

After extracting icon from EXE file, I convert it to bitmap file.
In the option of popup menu, I click the [TBitmap] and then select the
bitmap file.

When I run the program on my PC, the bitmap on the popup menu has a white
background.
If I run the program on other PC, some PC get gray background while some PC
even get black background color.

Where can I control the background color of bitmap on the popup menu?

I wonder if the bitmap created is in the wrong color of background. However
some PC get gray background.

Any idea???

pc