Hey! It’s not going to break your game, if that’s what you mean. But my custom skins are geneticized around my defaults, and if you use different defaults, you may wind up with incorrect genetics, so to speak. THIS TUTORIAL explains everything you’d need to know – it’s what I used to geneticize my skin tones, and it’s written so that even someone with minimal to no SimPE knowledge could follow it. 🙂 (Not saying you don’t know SimPE! But for a lot of people, myself included, the prospect of messing around in SimPE can be daunting. So I’m here to reassure you that if I can do it, anyone can!)

Basically, skins are geneticized on a scale. The four default skins have assigned values of 0.1, 0.3, 0.6, and 0.9 (going from S1 to S4). To geneticize skins, you would go into SimPE and assign them a value around each of the pre-existing default values. So if the custom skin you want to geneticize is lighter than your S1 default, you would give it a value smaller than 0.1. If your custom skin is a shade between S2 and S3, for example, you could give it a value of 0.4 (or 0.45, etc.).

So I took all the custom skin sets I wanted to use, and in a notepad file, I arranged them in order from lightest to darkest, then set about assigning values on the scale to fit them around my defaults. Here is part of my notepad file:

My default S1 skin is the lightest of all the skins I have in my game, so I started the scale after 0.1. Everything between S1 and S2 are skins darker than S1, but lighter than S2 (ordered to the best of my ability – it gets tedious clicking back and forth in BodyShop, and depending on how many skin sets you’re using, it’s often hard to discern if one is really “lighter” or “darker”, as sometimes it’s just a different shade :3). 

Long story short: skins are geneticized around the defaults. If you use a different set of defaults and your S2 is lighter than mine, for example, some of the skins I geneticized with numbers less than 0.3 may be darker than your S2. So if your S2 and S1 Sims have a baby, it’s possible the baby will be born with a skin darker than either of the parents. Does that make sense? I’m not very good at explaining things, it seems. 😐 (Here! Go read @vimpse‘s post! She’s better at explaining than I am. :D)

Again, mixing my geneticized skins with different defaults will not break your game, but if you’re OCD about genetics (like I am) and having babies with darker/lighter skin tones than both of their parents would bother you, then I’d recommend picking the custom skin sets you’d like to use, and assign genetic values in SimPE yourself to fit them around your defaults. 🙂

That’s why I did it in the first place, honestly. I use a lot of the same skins Vimpse uses, but I wanted to use different defaults so I set out on a skin-geneticizing expedition of my own. ;D

I hope this helps a little bit! I can’t overstress how helpful this tutorial is, so I’m going to link to it again! If I can clarify anything else for you, drop me another message or IM me or whatever tumblr is making us do these days. 🙂