So I’ve seen a lot of people grow the strains I ...

Beginning week 6 start watering with cold water, not freezing. You can also put some ice cubes on top of the soil at night.

You will usually see some color change towards the end of flowering once the buds hit their final ripening stage. At 3 weeks in flower the buds are just starting to really stack up. You can decrease your night temp below 60f during the last couple weeks of flower and it will usually bring out some purple color. But this color change comes from a lock out which really doesn't benefit the end product of your plant. Just keep her in a proper environment with good care and you will end up with some nice fat potent buds. If you focus on color then you might do something that will decrease the quality of the end product. Good luck in flower!

it is still early unless you are growing an originally purple/black colored strain. Otherwise If there are colors in their genetics,you can make them appear with the help of cooler night temps in the final phase of flowering. Try to create some temperature difference between day and night like 8-10C and you'll see the colors you are looking for.but only if it is in the genetics.