For the example I shall use B to be chr(2) C to be chr(3) ect.

C03B"Welcome to "CBC12B"My channel!"
C03B"Welcome to "C12"My channel!"

I often use alias like
alias e1 { return C03B $+ $1- $+ CB }
alias e2 { return C12B $+ $1- $+ CB }

$e1(Welcome to ) $+ $e2(My channel!)

But this doesn't actually need to do the closing colors if its just going to start them right back up.