1.) Make a copy of webuild.exe and open the copy in Resource Tuner
2.) Unfold the "RC Data" folder in Resource Tuner. (This contains various views)
As an example I modify the background color of the "About" dialog
3.) Unfold the "TFMABOUT" folder. and select the first entry (fmAbout: TfmAbout)
4.) Now you can modify various properties like the backgroundcolor (Color) or the text color (Font.Color)
(You can find a list of VCL color names here:
http://docwiki.embarcadero.com/RADStudio/XE8/en/Colors_in_VCL)
5.) Select the "Color" property in the right window.
6.) Change the value in the requester below the property window to "clRed" or whatever you want.
7.) Save the file.
8.) Open your copy of WeBuilder and select the "About" menu item.
9.) The background color should now be red. (Or whatever color you selected in step #6)