I believe you may use BBcode along with some string treatment, try passing something like "[color=#FF0000]A[/color]lphabe[color=#FF0000]t[/color]" as a string to a Text object.
You may declare the color inside a variable first and call it dynamically:
C0 = "#FF0000"
"[color=" & C0 & "]A[/color]lphabe[color=" & C0 & "]t[/color]"
For the string part, suppose you have:
S0 = "Alphabet"
You can then use mid(S0, 0, 1) to get "A" and mid(S0, len(S0) - 1, 1) to get "t".
Of course you can do that dynamically too, or whatever way suits you best.