Dont worry so much about the hair color, Buy a powered microscope, the handleld kind that you can buy on internet or at head shop , Mine is a ECOPLUS iluminated microscope 60X - 1000X it was only $20 and look for the trichomes to curl and form little bubble heads that are murky.. When most of them are like this then harvest. I have grown some sativa strains like super silver haze that went 15 weeks and still had very few read hairs but the trics were ready and it was some dank shit once it cured and we smoked it... Depending on the pheno it might not get alot of red hairs.. I have not grown this strain but curled thricomes with bubble heads that are murky means that any strain is ripe..