faded colours after export in RUSH

Hi all,

when exporting a video from RUSH it comes out really faded and washed out, checked a couple of other users questions on this but no real answer to it. 

screenshots attached, the bright one is working in RUSH, the dull one is a screenshot after

can anyone help with any suggestions? its like going from RGB to CMYK kind of effect tho i know thats impossible but just saying, it loses all brightness and vivid colours. really weird. it must have something to do with new imac, i upgraded to 2020 imac 27" at the start of January, it doesnt happen on my old 2013 imac. is it the colour management of the new imac? cant find to change within rush, and all export options are the same result > really appreciate anyones solution as it looks a bit crap. thanks in advance...