u/holdallthatremains

hi! as the caption says, i bought this shirt from vinted and on the photos on the listing the sleeve part of the shirt looked grey, but instead they are this muted blue, i think it would be super cute and match a lot mire of my clothes and style if they were grey like i originally thought, how would i achieve this?
the label says its 50% cotton and 50% polyester.
ive never dyed clothes before so im pretty new and unsure what ive doing, and i’ve definitely never tried to turn an existing colour into a different one, so any help would help appreciated
let me know if you need any more info! and thankyou if you do help me!