I had the same er and pr positive her 2. I did the same chemo as you with cold cap, finished chemo in March of this year. Unfortunately the last two ac chemos I got massive headaches and had to stop cold cap before the full time was up so consequently lost a lot more hair, I didn’t lose it all so I now have a short curly mess 😆
My hairdresser is going to discuss with me next visit in a couple of weeks about putting a color in before Christmas.
I think at some point it was mentioned to wait 4-6 months before colouring, more if you want to bleach.