In terms of selecting a background for your discus show tank you have many options to choose from.
Black is a good option as it allows for the highest visibility of the discus, showing off all their magnificent colors. However, you may also choose green, red or blue. Just remember not to use a like colored background with a like colored discus, as it won’t create a very good effect at all.
Some discus keepers opt to paint on the colors for their background using some form of marine paint, while others use tiles made out of cork as a background.
You may wish to consider not only providing a background for the discus show tank, but also covering up the sides as well. Not only does it put emphasis on the main attraction, but it also gives the discus a sense of security as well.