Crystal Reports-Need way of specifying multiple unnested IFs in formula

I am filtering out substrings in a database comment field with the following example code:

if InStr({MyTable.Comment},"Red") = 1 then
    replace(replace({MyTable.Comment}, "Red",""),"  "," ")
else if InStr({MyTable.Comment},"Blue") = 1 then
    replace(replace({MyTable.Comment}, "Blue",""),"  "," ")
else
    {MyTable.Comment}

This works perfectly if "Red" is in the comment in one row and "Blue" is in the comment in a different row, but what if "Red" and "Blue" are in the same comment?  Plus, there may be other substrings in the comment that should not be filtered:

DATABASE COMMENT       PRINT ON REPORT
Green                                 Green
Red
Blue
RedYellow Green              Yellow Green
RedBlue                          
BlueYellowRed                  Yellow
Yellow Cyan Green           Yellow Cyan Green

I really need the ability to have independent, unnested IF statements in the formula:

if InStr({MyTable.Comment},"Red") = 1 then
    replace(replace({MyTable.Comment}, "Red",""),"  "," ")
If InStr({MyTable.Comment},"Blue") = 1 then
    replace(replace({MyTable.Comment}, "Blue",""),"  "," ")
If none of the above   <-- pseudocode... unsure of how to specify this in exact code
    {MyTable.Comment}

or (in pseudocode, kind of)....

If substring of comment contains "Red" or "Blue"
       if InStr({MyTable.Comment},"Red") = 1 then
          replace(replace({MyTable.Comment}, "Red",""),"  "," ")
       If InStr({MyTable.Comment},"Blue") = 1 then
          replace(replace({MyTable.Comment}, "Blue",""),"  "," ")
else
    {MyTable.Comment}

When I do this, however, I get the error, "The remaining text does not appear to be part of the formula".  How can I filter on multiple, independent conditions?  I can't specify all the permutations of color combinations that could be in the comment - there would be way too many.

Important Note: There will never be the condition when the same color appears twice in the comment string:
RedGreenRed  <-- won't happen
BlueBlue Blue   <-- won't happen

In lieu of sugestions, can you please respond with the exact code and an explanation (if any) of why it needs to be done a certain way.  Thanks in advance.