This rare medium yellow-orange color is made from 44 2x3x2 Container Cupboards (4532.dat). These are
available in the Harry Potter Sets #4732
Warthog's Classrooms or #4723 Diagon Alley™ Shops. I happen to pick them up from
Amazing Bricks on
Bricklink.

Here is a sample of the difference between med yellow-orange and orange (your
visual results may vary)...

This is medium
yellow-orange...                         


This is orange...                                                 

Here's a shot of two of the real ones in context.	This is a picture that I used to model the box car after.