This is what I would call a definitive Paper Mario story. The partners all have unique personalities while still sticking to the basic rules. Each world (although only two) has already separated themselves from the others. I'm slightly interested in the villain, and, which I'm thankful for, separated the plot from other fans. You aren't dabbling in TIME, and legitimately trying something different. While Color Splash did dabble with this, you're doing more with it, and I'm eager to see you pursue this. However, You asked for constructive critisicm, so here you go...
The villain is, how do I put this, bland. He doesn't seem to have a reason for wanting to rid the world of color, he just does. Of course, there could be a reason for this, and you haven't explained why, kind of like Temple of the Sun. Another is that you are guilt of 'deus ex machina.' If you don't know what that means, it's basically this: Someone hits a roadblock, and something appears to save them or destroy said roadblock. Examples of this are Goombria (Did I say that right?) deciding on the spot to save Mario, the Goomba Troop just appearing and deciding to help Mario, the professor just happening to know where the brush was, etc. A little of it is OK, things are bound to happen just through luck, but try not to fill the story with it. Another thing, albeit minor, is still present. There doesn't appear to be a definitive hub. You appear to be trying to make it still seem like the game, doing things like File Loaded. Mario doesn't appear to have The Rest Stop, like Toad Town or Rogueport. Again, minor, but you should still have an area for him to rest in case it is based around being both game and story. But, it's not like it's required.
Whew, I'm done. But overall, I'm excited to see this story unfold. Keep writing, and make this an astounding story.

I've really enjoyed this so far! I will admit that the call to adventure came off as quite similar to Temple of the Sun and that had me worried initially, but you very quickly shaped this into a highly unique story. I'm really liking Chapter 1 so far, Koopa Keep is very different from anything I've seen in a Paper Mario story, particularly as a Chapter 1 location. Also your description of the famine was very striking and sets a fittingly desperate undertone. My only complaint would be that Lukas seemed to come a little out of nowhere before joining. I think it would have been a bit better to give him a little more time in the story before having him join. It doesn't have to be much, just something like showing him beforehand or having him bring Mario and Goombrianne somewhere and talk to them a bit more about what's going on.
Looking forward to reading more!
Viva

Ah I remember you talking about this guy. I guess from this part I can't really tell what his personality is supposed to be like though. Maybe add something in his bio? Remember Mario's partners are all pretty vibrant and over-the-top.

Hmm I bet they need a Koopa to hit the switch. Is that captain going to be the next partner?

AHHH. I love this story! It's such perfection! It's easily becoming my all-time favorite Fanfic, and I've never even played Paper Mario! You're doing such an amazing job, you should be drastically proud of yourself.

NO ONE SEES THE WIZARD.

Hypothetically.

Hehe. I loved it! My favorite chapter so far. Nicely done!

Keep it up!

It was cool to check up on the other characters, I quite appreciate that. As always the writing is seemingly flawless! Some parts at the beginning seemed a bit repetitive when you were talking about everything being gray. However, that is no matter.

Keep writing! I'm enjoying this story A LOT.

Sorry i didn't review!I was busy with my own story..that i took two months to finish a rushed chapter, woo.

Well we're not here to talk about my story , we're here to talk about another amazing chapter! Man That part with Goombrianne kinda scared me, nooo she won't die! And i LOVED those Goombas that saved Mario and Goombrianne!Mario can now summon Bowser's Minions help in battle!XD!The Chroombas were kinda scary as well.. Goombill RULES!And that part where Mario and Goombrianne hugged..man i felt it right here :D.

Thanks again for such an amazing chapter!I'll be looking forward to the next!

Another nice chapter! I was glad to see that there was more description than last chapter, although that barely means anything. This story is unfolding nicely, and I'm loving it! Every chapter has been so epic, with new things thrown at you, and it's so interesting and exciting.

Keep writing!

Awesome, awesome chapter! It was a good mix of dialogue and description; it was definitely interesting and immersive.

I really wish I was familiar with the games to know who the OC's are and whatnot! Anywho, you're doing a good job with all the characters, and I'm growing to love everybody! CAn't wait to see where this story goes.

Keep writing!

Huh!This is pretty interesting!And Temple of the Sun?Hah, you've read that amazing story?It could really be the next Paper Mario game, yours too!The idea of everything except Mario and his partners to lose their colors is very interesting!And i've ALWAYS wanted a Para-Goomba as a partner!I love her!And Professor Goombella?Nice touch!I'll be looking forward to the next chapter!

This story has nice dialogue! Every character is interesting and unique in the way they talk, so that's great. But I find myself wanting more detail on the setting and a bit less on dialogue sometimes. But, that could just be that there isn't much setting to talk about yet too. Good story so far, keep it up!

Awesome! It seems like everything so far in this story is so perfect, it could easily be an actual game. Nicely done with that, good sir!

I'm thoroughly enjoying the story so far, and it seems like things are really picking up; keep up the good work!

Keep writing!

Ah thanks for the shout out XD I guess Mario deserves a less difficult Goomba partner this time.

Yet another awesomely amazingly story!

As I've stated before, I'm ridiculously impressed with the originality in the backstory! It's so interesting and EPIC. OH SO EPIC. And it makes me crazy excited for what is to come!

The dialogue was so entertaining and engrossing. Something about it just made me continuously read, and I loved every second of it! I love Bowser's character...Which is weird considering he is the bad guy, after all, but still! Love it. And Kammy, of course!

Ahhhh, everything about this is amazing. Seriously, keep up the good work!

Keep writing!

Ahhhhh, how exciting! I hope you update soon!