How to draw a colorpicker on HTML5 canvas?
I created a solution for you on HCT. You can see it here:
http://www.html5canvastutorials.com/labs/html5-canvas-color-picker/
The idea is to find a color picker image that you like and then draw it on the canvas. On the mousedown event, we can get the mouse coordinates and then use the image data of the color picker image to pick out the color.
Hope this helps!