When you want it to be colorful, to full with joy and happiness ... Then you can color a brighter color... Every color actually significant of different situation or mood.
If you would like to color the paper red, then it will become red, if you like rainbow, then you can always color it rainbow color... you're the one who decide the road of your life... no can make you color green while you want yellow...
When you have draw it wrong, then you can tear it off and start all over again.... to change the black to colorful color... Life are just like drawing, that is what it say in chinese... when you color if well, it will become a great painting, when you have no direction, it become mess....when you're not careful, you mix the wrong color then become ugly~ Color selection is very important ...
Make sure you use the right color to color your paper, so it will be a great painting that make you proud....