This is something I worked out while I was approaching lvl1000. It might look confusing at the start, but let me explain, it's pretty intuitive and rather fool-proof.
Big mana cycle consists of 15 "choices" before they start repeating (in my picture, from red/yellow to next red/yellow), first "big cycle" has grey background to easier spot when the repetition occurs. There's 6 mana colors, so to keep things "even" every 6 levels you need to create pick-order for two Big Cycles = order of 30 "choices".
You can find yourself on my list if you level your mana evenly (as long as nothing it two lvls apart, you can find where you are in the table, and follow it from that point. Else just use your "intuition" for a few lvls (rule of thumb, pick the one you have less lvls of) until you get all colors within 1 lvl spread (i.e. everything lvl 53-54 or 75-76 or 101-102).
If you are at the point where all your mana lvls are even - check what your next pick is and find the correct Small Cycle (from the point where all mana is even, next choice will be one of the top ones of the small cycles). If you have all mana within 1 lvl spread, when you get the next choice, just check how many of the mana colors are higher lvl (i.e. if two are higher than the other 4, then it's the "3rd choice" of a small cycle, just look at the 3rd places in small cycles - find the choice you are given now -> gz, you found yourself in the table, from there on just follow the order).
You can use the same way to find what to pick next every single time (if you have short memory or can't be arsed to write down where you are right now).
If you follow the table, you'll have even mana masteries at lvl 1000 (the last 6 lvls are the first "small cycle", ending with the Blue/Yellow choice).
Fun fact, you actually get to pick once more at lvl 1001, so you get to pick between red and purple, the one and only mana color that will be lvl168 for you the rest will stay 167. IT SHALL NOT BE EQUAL.
I tried to explain my system, but I feel like I only made it more complicated than it is, I hope it helps anyone at all. And if someone has any questions - just post or pm.
PS. I know it's not exactly the topic for this, but that's what ppl talked about and I see no reason to necro a 2 month old thread or make a fresh one, again.
e/ oh right, yes the one to PICK is the bold/underlined one.