How can I colorize text within square brackets please, like [fu] ?

I need them colorized as they will hold reminders for myself at that position whilst I'm writing.

Thanks
Sharon.
-- 
A taste of linux = http://www.sharons.org.uk
TGmeds = http://www.tgmeds.org.uk
DrugFacts = https://www.drugfacts.org.uk
Debian 9.5, fluxbox 1.3.7, emacs 26.1.91, org 9.2.1