Exporting to powerpoint from Keynote changes colours

I am going crazy trying to figure out how to preserve colours in a Keynote presentation. When I export to Powerpoint, the colours go duller and lighter. If I reopen the exported PPT file in Keynote, I can see that the colours are different from my originals.

I tested exporting to PDF to see if that would have the same problem, but it does not. The colours only change when I export to Powerpoint. The problem is the same whether I export to .ppt or .pptx.

Is there any solution for this? It looks like people have been asking about it for years but I can't see any explanation for it. I'm attaching an image comparison from both (Keynote on left and exported PPT on right). The colour change is a serious problem for brand colours.