I'm not sure there are any AMA standards regarding runway markings outside of competition rules.

Here's a link to the AMA online documents...

http://www.modelaircraft.org/documents.aspx

Our runway has a white center line, yellow "X"'s at both ends and a midpoint line (also white).

We have markers in the flight area that define the "box" for the pattern flyers as well as a "pilot box" for them to practice from.