A mixed tattertint from the Headmaster is 250 gems?! lol that'll take 8-9 months relying on the attendance quest...
I'm not sure if Iris will give me a Colour Wonder quest yet. Probably need to do ~50 more quests for her.

Don't worry Quinineer, it definitely won't take that long!
I made this board four days after Iris's quests were activated, and got my first Tattertint the next day~

The special colours use 4-5 basic Tattertints, so it shouldn't take too too long to get there!

Yeah, remember you can always trade the colour wonder tatter tints up, you don't NEED to buy the fancy colours. It's one of the reasons I really love this site. <3