If I was to patch it and then paint would it look mint?It’s hard to patch mint, so you may be waiting a while.
Mask up the surrounding area, put on more than what you need to scratch back flush.
Get your timing right, ie same time as you put in on originally, as different timings will effect colour.
I had the same thing with thick custard I added more milk but it was still a little custardy?If you use paint then Rendit can supply and Parex do a colour wash. Jub revitacolor is good as well. These paints come very thick and need watering down a lot if it is to be a colour wash and not look painted. I have added 40% water to jub and it was still a bit like paint.