Highlight the data set. Go to the Home Tab. Click Conditional Formatting. Click New Rule. Click Use Formula to Determine which cells to format.
Enter this formula:
=OR(A1="BBBR",A1="BRRR",A1="RRBR",A1="RRRB",A1="RRRR")
Click Format... Change the font color or fill color to red. Click ok. Click ok.
That should work.