|CORIO2 scalers use YUV (YPbPr) signals for internal mixing and image generation.|
If you want to convert an RGB colour value to the respective YUV values for keying and background colours, then use the following Excel spreadsheet:
Customer YUV calculator 1.xls
Note that there are 2 colour-spaces that can be converted to, depending on your output resolution (NOT your input resolution).
See also YCrCb values for various colours if you cannot open this file.