Most of my horses at higher tiers lined up for a shot at the black Tier 7. The parents had a combined black value of "8". I got it on the exchange of those parents after resetting the female, and the other two were tier 6's with high black values including a tier 6 purebred black. Now that I have this one tier 7, I have spent a bit of time back breeding lower tiers to see if I could produce some Tier 5's that would provide a "7" white and/or red combination value. I finally have two tier 5's that have a shot at the red tier 7 that i'm going to level up to 29 each and give it a go.
I'm not breeding any tier 6's until the non-purebred 7's are unlocked and available. It's just too much work leveling tier 6's for a small shot at moving up a tier. I'm happy getting 6's from 5's if I miss the tier jump to 7, but would not be happy getting 6's from 6's.
So...the short answer is yes...i'm still trying for 7 purebreds, but only from tier 5's with the combined color potential.