If you evaluate or print the following string you get what you want:
"\!\(\*StyleBox[\"text\",FontColor->RGBColor[1, 0, 0]]\) \!\(\*StyleBox[\"text\",FontColor->RGBColor[0, 0, 1]]\)"
This is a single string and it contains color information for different substrings.
Do[Print@"\!\(\*StyleBox[\"text\",FontColor->RGBColor[1, 0, 0]]\) \!\(\*StyleBox[\"text\",FontColor->RGBColor[0, 0, 1]]\)", {5}]
