Achtung!

"Jack The Ripper? No, my dear.

Closest match: Psylliodes chrysocephala genome assembly, chromosome: 4 Common name: Cabbage Stem Flea Beetle

i got a similar ask about this a while back and i've been working on something to better explain what i mean because i'm not too happy with that guide anymore so i'm just gonna address both here!

in my original post i talk about choosing analogous colors rather than using layer settings, but you guys are asking about multiply layers so let's talk about that since frankly they do save up a lot of time and headaches AND they can help understand color more easily so we can pick the palette from scratch next time.

right, so we have our guy.

in the sunset example, a deep orange multiply layer would look something like this:

however, in my previous guide i said that usually warm lighting means cool shadows. this isn't always the case, however, because the color of your shadows are determined by your environment and bounce lighting. shadows on their own have no color because they're just absence of light, so the color we perceive them to be is what's being projected onto the subject.

this same sunset with cool shadows would look a bit like this:

if that looks more natural even though it doesn't match the orange of the background, it's because sunsets only look orange around the area the sun is in the sky, so the color of the sky that's facing our character here would not be projecting an orange glow onto him.

while it's not a hard rule, like i said, usually warm lighting comes with cool shadows. i think it's also worth keeping in mind that reference photos can look very different from one another because of editing, exposure levels, filters, weather and time of day, etc. so also take your own outdoors observations into account. always observe colors when you go outside if ever (don't be like me)

here's another sunset example except the sunset is now behind our viewpoint and facing the character from the front. he's not fully lit up, perhaps he's standing under something where the sun light doesn't reach him directly. i used a red glow to indicate sun this time only because i think it looks cool with the teal sky:

now addressing the ask with the "pikachu in a green house" example: yes, i suppose using a multiply layer that matches the color of the environment works. after all, like i said up there, shadows will usually reflect the color of the surroundings the subject is in.

this was a lot of blabbing about colors and i didn't even touch on values which is also super important!!! but i'd like to do some studies before i talk about that to make sure i'm not talking out of my ass. hope this helps though!!