To answer your questions:
1. Water inside levels remains static and cannot change during gameplay, so unfortunately that is not possible.
2. It actually does use RGB, but it is different regarding how you use it. There are 4 values, separated by commas. Each can go up to 255, and down to 0. The first value is opacity, and the other three following afterwards are the RGB values.
Hope this helps!

oh dear that would be awesome if the water not static, cause in my new level i already make a cookies gooballs. the level is like this put cookie balls to alice mouth. there is pipe and a few gooballs with strand but its at bottom so you need fill it with milk so the pipe could suck the cookie balls. but thx for color code its really help me. now i need another way to use my cookie balls...

I'm a bit late but if you wanted to make dynamic water you might be able to achieve it using tons of goo balls. Those gooballs could kind of act as water drops. You could disable interaction with them and give them a solid color that has a bit of transparency. You should give it a try and see how it goes.

what do u mean act as water drops ? but they still circle right just like other gooballs. and what exactly function of "disable interaction". im still not understand all the function

So if you had a bunch of them together you could make them act as the water. You could try making the image for the ball bigger than the actual ball so there are not any gaps and it looks more like a liquid. And by disable interaction I mean not allowing the player to drag them.

i already do that but the problem is what picture i should use so its look like a real water. circle ? and how about the size. if i use bigger scale than it will out of tank. cuz my plan is to put it on tank that could drop