It'd be great to implement masks to make coloring, shading, and effects of any drawing easier.
Having a hierarchy of masks within masks would be super helpful too.

So I can do, for example:

• Make a Color layer. Duplicate it, create a mask out of it called 'Color Mask'.
• Put the Color within the mask.
• Create a Shadow layer within the Color Mask layer to apply shadows liberally.

Color Mask
...... > Shadow
...... > Color

• Make a Shadow Mask within that so then I can tweak bounce lights or effects with soft brushing.

Color Mask
...... > Shadow Mask
............ > Shadow
............ > Bounce Light
............ > Core shadow
...... > Color

Allowing me a deep hierarchy of masks will make coloring and shading much easier for myself and others, in addition to other practical applications.

Transparent Pixel Lock is a tool that takes the alpha values of a layer and locks them, but it will allow me to change the color of the pixels as I so please. It will just give me another took at my disposal that will make my life so much easier to paint and animate with pixels.

If you ever need help visualizing what masks are or the applications it can have in animation in addition to what Transparent Pixel Locks are, feel free to inquire and I can provide detailed explanations with illustrations!