The GBC & SGB both support colo(u)r. Is graphics programming for them similar ?

Not really. They both have in common the ability to display graphics written for GB pocket & GB classic but that is where the similarities end.

The SGB is able to colo(u)rize GB games using primitive techniques that involve sending information to the SNES/Super Famicon. As such, if you attempt to scroll the screen it is sometimes a slow process to send new information to the SNES so colo(u)rized, scrolling screens are difficult to implement.

The GBC, on the other hand, does all colo(u)rizing itself using totally different methods. As a result, colo(u)rized games written for the GBC will not work on the SGB & vice versa.