just something i'm working on..

[Vipershark]

Allow me to clear something up, before I go any further. I've had to learn everything I know on my own. I have never had help, and there were no college courses to take on the subject. So everything you see in my sprite work has come from 11 or more years of figuring it out for myself.

That's fair! A lot of us here started out by learning on our own and then later learned the correct way to do things.
It's okay not to have formal art training and it's okay not to be fully knowledgeable of all the techniques and stuff. Everyone starts somewhere.
What's not okay though is to say "okay but this is my way of doing it, I don't care if it isn't correct". Whether or not you agree with what's being said, you should keep an open mind to criticism.

Such as with 'pillow shading'. You all seem to treat it as a negative thing, here. I could be wrong, but pillow shading has its uses, and have have very positive results.

There is a very few number of situations where pillow shading is the correct technique to use and even fewer situations where it actually looks good.
Pillow shading occurs when the lightsource is directly between the viewer and the sprite, straight on, and even then you don't necessarily have to pillow shade to show that.
I'm no expert in shading so there's no way that I personally can make a good example to prove it, but 99% of the time pillow shading looks bad because there are very few reasons why the light source would be coming from the viewer, meaning that it's out of place when it's done.

I'm not going to go into why I'm rather liberal on the number of colors and shades I use, just because this would end up being a rather large TL;DR,

I honestly kind of wish you would, just to see what kind of viable explanation there is for it.

however, I would like to challenge you to edit my sprite the same way you did with Zye's Jason, without brightening him, as he is meant to be a near-black, sapphire color, and without dulling him down. He is meant to be very vibrant. I did the best I could with what I've learned. There's no way to hue shift him, as he is far too dark in color for that, and much like Zye, I'm not willing to budge more than a few degrees on his brightness level.

That's not really a challenge I can take up, and there's a simple reason why: light doesn't work that way. White light is made up of an entire spectrum of color. It's not just "white", it's actually red, orange, yellow, green, blue, indigo, and violet all mixing together in various amounts to create the colors you see.
Of course the possible level of hue shifting differs on a case by case basis, but generally speaking, hue shifting is always possible because light is made up of different hues. If you look at something white, its darker shades aren't just darker versions of that same hue. If you look at something black, it's not just a flat sheet of one hue.

I'll give you a real-world example of the closest thing that I have to a "dark blue sapphire, almost black" color to show you how light works.

big pictures

This is my wallet. You can see that even though it's a very deep and dark blue color, it still has bright highlights and dark shades in it and lots of contrast so you can easily see the details. (I have these in GIGANTIC resolution if necessary)
"But that's under a sun lamp so it's a lot brighter than it would normally be! That's not fair!"

Okay, I'll accept that point.
So I took a picture of it with the sun lamp turned off and using the regular incandescent light in my room.

"That's not natural light, though! The sun wouldn't make it look like that!"

You're right, so I went outside and took pictures in natural, non-direct sunlight to show that it still works the same way:




Even though this is a bad way to make a palette, I picked out colors directly from part of the image just to show that hue shifting occurs naturally:

If you zoom in, you can see that the wallet isn't just blue; it's made up of a whole rainbow of blues, greens, purples, and other hues that give it the color it has.

As you can see, light naturally has highlights and shadows, and it uses hue shifting and contrast to make details visible.
Color is actually three-dimensional. You're changing brightness, but you're barely touching hue and saturation, causing your colors to look flat (since they're quite literally one-dimensional).
If you want to make your sprite more vibrant, the only way to do so is to make it so that all your shades aren't so indistinguishable.