Somewhere on a pentax website there is a brochure called Lenses and Accessories.
On page 28-29 there are some nice drawings of the lens layout i the DA lenses.
I have uploaded the drawings for easier access here:
Pentax smc DA lens construction from pentax brochure - Imgur
Some of the elements are brown, green or blue. I think blue means ED and green aspherical.
There are brown elements in the 55mm and 18-55mm - anyone knows what they are?
I like these kind of schematics. Are there similar collections of drawings for other lens series?