Purple interveinal chlorosis?

So I'm not going through listing everything to do with my grow, I'm just curious what purple - not yellow interveinal chlorosis means. I've seen some finished grows where half the fan leaves are almost purple in middle or along the edges. So I'm not too concerned being 2-3 weeks from harvest. I tried to Google and all I found was it's necrosis??

No worries!

I get concerned when I DON'T bring out the colors at the end of a grow. haha.

Thanks fellas! I did some more googling and didnt find a definite answer, just that various strains do different things at the end of flower and its not uncommon.