From seeing multiple tools made for the sole purpose of making Mr. Game and Watch recolors, I've decided to see just what gives him his colors. Well after a bit of digging through his model file, I've found what gives him his colors and outline. Two CLR0 animations give him his colors, one for his body, and one for his weapons. This tutorial will show you how to recolor Mr. Game and Watch without any outside tools.
What you'll need
-BrawlBox [I highly recommend any version from v0.76b and up (current version is v0.78)]
-A FitGameWatch00.pac file.
This tutorial is surprisingly not a complex one, so there shouldn't be too many steps. (Pro Tip: To enlarge the images used in this tutorial, just click on them)
1.) Recoloring an Existing Slot
1a.) Body Color + Outline
Start by opening your FitGameWatch00.pac in BrawlBox. In here, you'll be looking for two different AnimationData[0] entries, each of which have a single CLR0 animation named FitGameWatchColorAnim and WpnGameWatchColorAnim respectively.

We'll start with Mr. Game and Watch's body first, so open up the FitGameWatchColorAnim entry, and you'll see 5 Material entries (AGameWatch, BrdDSGameWatch, BrdGameWatch, BrdZOffDSGameWatch, and BrdZOffGameWatch). The AGameWatch Material entry controls his body color, while the other 4 Material entries control his outline color.

Open up the AGameWatch Material entry, and click on ColorRegister0. Here, you'll see his primary body colors (each Frame is its own Costume Slot). Double click on the slot you want to recolor, and a new window will appear. In this window, you'll only be touching the R(Red), B(Blue), and G(Green) values. After you've inserted your new color, click Okay.




Next is his outline. Open the BrdDSGameWatch Material entry (or any of the other three), and click on its ColorRegister0 section. Here, you'll see his outline colors that are basically a lighter shade of his body color. Do the exact same thing you did for his body color, except use a lighter color. Now use this exact same color for the rest of the Material entries in the FitGameWatchColorAnim animation.


To view how your color will look in-game, open the model viewer, change the animation format to CLR, select FitGameWatchColorAnim animation, and go to the Frame your edited costume slot will use [Ex: 01 will use Frame 1 (shows up as Frame 2 in the model viewer)]. If you're not satisfied with your edits, you can edit the Frame itself in the Model Viewer until you're satisfied. When you're satisfied with your colors, move onto part 1b.

1b.) Weapon Color + Outline
2.) Adding a New Recolor Slot
Even this this was a bit of a niche issue, I hope this helps those who needed it.