Thanks for the query.Colitis
may be related to darkening of palms and soles.
It may be related to peutz jeaghars syndrome.
it is a condition related to colitis and darkening of palms.
If possible get his colonoscopy
A photograph would have helped me in giving a closer diagnosis.
Please meet a dermatologist
and discuss regarding this.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.