Well, this probably should have gone in the mkwii section...since this is more about board problems, but I'll answer you anyway.
It really doesn't matter what color the light on your wii is. When it's yellow, that means it's plugged in and turned off normally. It's supposed to be yellow. Yellow is the color of sunshine. You like sunshine, don't you? Of course you do. Everyone loves sunshine. Especially plants. Plants require the energy from sunshine in order to carry out a reaction to create glucose. You may know this process as photosynthesis. Here's the equation:
6CO2 + 12H2O + light energy -> C6H12O6 + 6O2 + 6H20.
Word up. You put Carbon dioxide, water, and light energy in, and you get glucose, oxygen, and water back out. So if you're ever needing some oxygen, just exhale on a plant while simultaneously pouring some water on it. It'll give you some oxygen in exchange for your kindness.
I believe I've provided you with a suitable answer to your problem. Contact me if you need further instruction.