Hi, I've recently begun playing sims 4 and noticed that only two of my sims of the same household have this issue where they look good in CAS but terrible in-game. The photos are shown below.
My specs are pretty good, I have a GeForce GTX 1050, 8GB Ram and an Intel i5-7300HQ @ 2.50GHz. My game runs flawlessly on Ultra. I'm not sure what's causing this but I'd appreciate it if somebody could help. Thanks.

Are you using specific custom content for these sims i.e. eyes, etc. If so have you tried with those taken out?

I removed all the CC and he still looked like that.

Am I missing something? I don't see any difference between the two screenshots besides the angle and the lighting

In create a sim, his face is more defined and has a lot of color to it whereas in live mode it's not. The glitch appears out of nowhere and has just done it again on a separate save to another sim.

I took it to photoshop so I could see it side by side, you're right, his face is much more dull in live mode than in CAS
could be a bad cc indeed, maybe something they are wearing/skin detail that's broken
if it's not happening with every sim you can narrow it down by seeing what you put on the sims who have this issue, different to those who don't have it

So sorry for the late reply! Narrowed it down to Slice of Life's face mask option Thank you so much for all did their best to help!