player and npcs rgba.
 

tilelayers[0].alpha
tilelayers[0].red
tilelayers[0].green
tilelayers[0].blue

We have these which allow us to change the RGBA of all tiles on a level, I think if we were given the ability to use these on the player and npcs in a level, it would allow for the creation of much desired effects, especially weather related, and day/night systems. IMO seteffect just doesn't do it, it looks ugly. I was playing around with tilelayers, and I believe the effects could be so much better with the ability to directly affect the RGBA of different people.

Some examples:
Setting the players Alpha could allow for a cloaking like effect.
Setting the players R G and B could allow for spell effects, like they turn slightly blue when casting a mana refill spell.
The world could turn darker rather than a dark overlay on the screen during day/night transitions.
The world could turn a bluish tint when rain starts up. (the previous two would require player and NPC RGBA setting along with the tilelayer RGBA.)
I'm sure others could think of useful things that could be done with allowing the RGBA of Players and NPCs to be set.

Both if possible.

You want to set the colors of each object separately or affect all objects on the screen at once?

Heard of the 'polygon' variable?
Use it.

Both if possible. It'd allow for a much better look than seteffect provides.

What the hell are you talking about? Are you suggestion is showpoly a quad over the screen and change the alpha and color?