I use as background color of a TextBox light green (128,255,128). It appears as expected in all renderings except XLS (old Excel 97-2003). In XLS the color is grey (128,128,128).

I observe the same issue when modifying the RGB numbers in some boundaries - the color in XLS is always grey. There are RGB values rendered as expected though.

The issue reproduces with TRDP and CS reports in the corresponding Report Designers.