ex7-05-about.txt, cr 11 may 2015by ralph
animating by hue

for HTML and CSS) color my be specified by:
	HEX, RGB, RGBA, HSL, and HSLA
but for the canvas, color must be HEX or RGB only
the easy way to animate color is to use gradients
so, we will do a linear interpolation from red to blue

see fulton & fulton pp. 61, 131

end