Islamic Geometric Patterns - Hexagon 1

This design is from the Mustansiriya Madrasa in Bagdad, Iraq - built in AD1227. While I can find photos of the Madrasa I cannot find photos of this particular design. What is clear is that the design work is done as carving in terracotta; colour is not involved. 

First, following directions:

Showing the infrastructure: 

The red lines show the repeatable shape:

The repeatable hexagon isolated:

The experiment with colour begins:

How it works out repeated - and then I have an idea about the centre space, which is confirmed by a little more investigation - and the colour experiment continues:

Single hexagon, with colour:

Copied and placed as tiles.