Maybe blended lines with colored outlines?  
Years ago, an artist I follow on Twitter named Cubesona made a post suggesting colored outlines,  
since that’s what he always does. Saying that stylizing for Black looks better than using straight Black for them.  
I tried it and that’s what I’ve been doing since; using a very dark Blue instead of Black.

Blend line

@alidan  
Gotcha! Thx for the critique and advice!

for people asking for single lines,  
drawing a single line that is good takes FAR more effort then combine ing tons of thinner ones. You need a good grasp of line weight and where to use it thick and thin, while tons of smaller lines like this give an approximate line weight and lets you see about what you want easier.
 
for artist  
if you want an opinion on the blended, try a bit more contrast where the lines would be, nothing that looks out of place but something that shows a line would be there more, especially because it is an ass the light source for the ass looks like it would be hitting about the cutie mark area, so there is no real reason the the inner left side of the crack would be as bright as it is.
 
If you want to practice lighting, try to find reference that has a singular hard light source when it comes to rendering lighting is a big thing you have to start taking into account and even a rudimentary understanding of how it works makes a night and day difference.
 
cant wait to see more of you stuff pretty much regardless of style you end up with.

Dat Rainbow ass

I feel like solid lines are better here, but only because it defines the shape more sharply. If you want less lines you could try using more contrast for a similar effect

Solid, 100%

solid

@LanceOmikron  

 
^ This

How about blended lineart with a very thin solid line on top?

I like the line version better

I feel like there’s a perfect medium somewhere between the two.

@Stitch  
Same.

i prefer solid lineart