I started with some fresh vibrant colors and tried the wet on wet technique (I feel fancy saying it) for the first time in my life. I was curious about how much of the blue pigment i could remove...

I let it dry for several hours and re moistened it, took a thirsty brush and stared working the oopsie magic:

crappy yellow light makes the paper look different color... but I was able to remove good amount of pigment! 

For the final colors, I tried adding highlights and shade:

The green circle has yellow light and blue shade, the orange one has yellow light and red shade and for the last circle... i just used the same removing technique again and exposed the lighter color from beneath!