someone requested a blue version of the equestria girls-ified Sixth Doctor

The original joke was that Six would the “Rainbow Rocks” version of Doctor Whooves, because of his tasteless multicolor costume.

This is the Sixth Doctor as he appeared in his later adventures (Post Trial of a Timelord) when he had mellowed out significantly. The costume can be seen in the webcast Real Time and on the covers of many of the Big Finish audio dramas featuring the matured Six