I have two columns of text...columns A & B

I want to combine the data in the two columns to form one column. Normally,
I'd use the CONCATENATE function. However, I want to record where the join
occurred without inserting extra characters.

For instance, if I color the text in column A red and I color the text in
column B blue; when I combine them, I'd like for the text to maintain its
original color so that the first portion of the string is red, the following
protion is blue. Alternatively I could do that with a font change at the
join point.

How could I achieve that?

Thanks