Finally got around to playing these, here are my thoughts of each:
Rainbow Land - Ok so starting off, the general idea is interesting. You're going around the world collecting different colours in each area, seems simple enough. The areas themselves have their own themes and mechanics which is neat, but sadly I guess that's all the positives there are. As far as a metroidvania goes, I feel like this isn't too great. Each area feels quite isolated from each other and nothing really connects up like a metroidvania should. Some of the ways to get the colour pieces are quite odd, like in the snowy area, how were you supposed to know you had to slash a random staircase? The general screen design is interesting I guess, but nothing looks too good IMO. I found countless tile errors with mountains and most tiles were used weirdly. I also really dislike the grey area, where you have to tank damage by running yourself into stairs to get through. That's honestly bad design IMO and things like that should be avoided as much as possible. Finally, I found the instakills early on to be quite cheap (dungeon entrances, cave entrances etc). At least reduce the damage they deal or something, but I dunno, I didn't like it. Overall, I didn't like this quest too much. It has a neat idea I guess, but the execution sadly wasn't good IMO.
NEW! - Gotta say, this was very fun to play, I enjoyed the demo very much! I can see you used the same tileset as the one from that Legend of Pokemon Warrior quest you made a while back. Really love that tileset and each area looks quite cool and unique in their own way. The way each area is all connected up was very nice and definitely felt very maze like at times. I do agree with Moosh though, maybe having some kind of fast travel item would be nice to avoid too much backtracking, but I generally didn't find it to be that much of an issue. One of the things I like about this quest is how you have a choice of items which completely change the direction of the quest. I went for the Sword first but I imagine if I went for the Hammer or Wand, I would have a very different experience and order. I definitely love the polish this quest has so far, and I'm definitely looking forward to this being finished!
Mage Quest - This was a really nice and short quest to play. It definitely has got some very interesting ideas and some really creative items. The quest itself was pretty nice and the tileset was well used. I can definitely tell this was quite rushed, but there was quite a bit of polish in some parts. I think the only one major problem I had was with that one teleporting item. I found myself getting teleported into pits at times, and the randomness of it is a bit weird. But generally that's all I really found. It would be cool to have more stuff in the overworld (like caves or secrets or something), but what there is already is neat. Definitely a nice quest, I would love to see this idea get expanded further if possible.
Vaporvania - Well this was definitely an interesting quest to play. First off, the screen design reminds me of a very simplified Yuurei/Hitodama, with the blocks and stuff like that. Each area kinda had their own "theme" I guess, which was pretty neat. I really like the progression of the quest, it nailed the Metroidvania feel quite a lot and I definitely love how collecting items in a different order affects how you travel through the quest (much like NEW!). Besides that, it was quite nice and fun to play through. As for the issues with the quest, I feel like the difficulty balance is a bit all over the place with my run. The quickman section to get the teleporter item is probably the worst part of the quest, not because of the quick lasers, but because of the obstacles that block your way which make it so difficult to travel through. I assume if I had that one item that blocks the constant moving traps, it would be a bit more bearable, but still I found that area to be quite bad IMO. The final boss was neat, and I definitely like how it makes use of some items you find throughout the quest, however I would highly suggest not to make the boss just teleport onto you with no warning. It honestly became so frustrating trying to avoid its attacks when it randomly decides to appear on top of you. Overall though, this was quite good and I enjoyed it a lot.