Fish Lips Kiss Heel, alternative coloured heel/toe socks - When do I change colours?

Hello! After some wonderful advice from you guys here, I have decided, to make it so that I have enough yarn to finish the socks I'm making, I will be using a different colour of yarn on the heel and toe.

I am using the Vanilla Latte sock pattern and subbing in the Fish Lips Kiss heel because it looks so much easier. (This is my first pair of socks.)

So for anyone experienced with the FLK heel, when should I start the new colour? When I'm making the 1" of regular garter stitch to start the heel, or once I start the kind of short rows section where the heel actually starts. I can't imagine the latter looking very good.

Thank you for your help in advance, this subreddit has been a life saver on this journey into sock knitting!