How to make releated products by reference number (p/n, index)

[PrestaShark]

Hi!

I wonder how to make releated products by product reference number (p/n - part number)
Ex.

 

Product have p/n 745gr

The first three digits describe model but second two describe color in this case gray
So i want to show all colors of the 745 model. ORange, BLack, REd, BLue, GReen etc

 

Any free or paid solution for this?

 

Thanks in advance!

Edited March 20, 2014 by kisweb (see edit history)