If you have hired your graduation gown, you will have to return it at the end of your ceremony but if you purchased your gown personally, you will be able to keep it.
The colour of the graduation gown depends on the academic level you’re graduating from. Doctorate gowns for example are generally red instead of black. Also, some universities will have a different colour scheme. For example, Anglia Ruskin's gowns and caps are navy.
There is a difference between undergraduate, Masters and PhD gowns. Undergraduate gowns typically have short sleeves, Masters gowns have long sleeves and some PhD gowns are red silk with silk and long sleeves.
You can take your own height measurements, and match it to a gown chart or the graduation company will carry out the measurements for you.