The function color_scale creates a color scale, or colormap, that is approximately uniform perceptually on both a color display and on a grayscale printer. The color scale is computed using the L*a*b* color space. It follows a uniform ramp along the L* direction, and it follows a semicircular path in the a*-b* plane.
The function color_scale_tool launches a GUI that allows you to experiment easily with different input parameters for color_scale.
How does applycform deal with colors outside the RGB cube? Certainly when you have lightness at 0 or 100, and non-zero chroma, these values cannot be reproduced by RGB. I've tried to implement a variation of this in Python (https://gist.github.com/endolith/5342521/) and it works pretty well, but you don't seem to do anything to limit the range of the colors.
I do not have image processing toolbox, so I cannot really run this code. But I give the submission a 5 based on your excellent post. It was really useful for me to learn more on how to work in Lab space. I modified the code snippet in your post and combined with cline and colorspace to display L plot using the resulting RGB color: