Changing the colour of a letter in a textfield

Hi,

I want to change the colours of individual characters in a textfield, after it already contains text e.g.:

Hello

// I have a function to change the 4th character red

[COLOR=Black]H[/COLOR]el[COLOR=Red]l[/COLOR]o

I do not want to overwrite the original Textfield but amend the font colour of a particular character.

Is this possible or can I only change the colour of the whole textfield and not the original character? Is there another better way?

Thanks in advance

Clo