If I hard code a text string in a cell, I can highlight part of the
cell and make the text red, for example, and then highlight the rest
of the text and make it blue.

I want to concatenate two text strings like =A1&" "&A2

I want what is in A1 to be red and what is in A2 to be blue.

I thought custom functions like =red(A1)&" "&blue(A2) might work, but
I can't figure out how to write the code.

Is a custom function the best option? Is there a simpler way? Is it
possible? Any help would be appreciated.

Thanks.
Angela