Yotsubato  6/10
White - Easy vocab, easy sentences. Don't listen to the "It has slang! You aren't prepared!", if the slang is common enough to show up in Yotsubato it's probably basic enough to warrant learning it.

Hanahira  1/10
White - There are like 5 lines in this visual novel that aren't spoken by a middle school girl. Don't cope about the colloquial grammar. It's just a bunch of ～ちゃう, you'll survive.

Axanael  -/10
Green - Haven't actually played this, but apparently it's like 95% voiced? Lots of action and snappy development, probably a fun read even if you're white.

Flyable Heart  3/10
Green - School life. Dropped it before the true route so I don't know if there were any advanced themes waiting at the end of it, but from what I've seen it's just extremely standard high school Japanese. You won't be missing much from going into it too early, so you might as well use it to level up to blue.

Rance Series  10/10
Blue - Funny green man sexually harrasses cute anime girl hahahahaha. Has some of the best games ever made among its titles. Fantasy vocab might wreck you at the start, but that's really all there is to it. Do the whole series for N1.

Little Busters  8/10
Blue - 90% of it is SoL. It'll still clown on you if you aren't used to colloquial dialogues, but you might as well use it to acquire that exact aspect of Japanese. Not very punishing in regards to whitenoising - it does have a lot of sub-plots with missable plot strands and details, but that won't have much of an impact on your understanding of the main-plot.

Subahibi  9/10
Orange - Definitely one of the harder school-centered works, but still a school-centered work. I guess you can make it blue if you don't care about Scaji's philosophy (but then why are you even reading it?). Pro-tip: engage with the text, actually look up references and at least make an attempt to understand what it's trying to convey.

Sakuuta  -/10
Orange - Same as above, also by Scaji. Easier than Subahibi thanks to a lack of schizo scenes, but not the kind of work you want to treat as a random piece of native material to study Japanese with.

Dies Irae  9/10
Orange - Not too bad for the most part, just a lot of chuuni monologues and the occasional verbose action scene. If this is your first advanced work get ready to learn about a lot of non-standard speech patterns you haven't run into before.

Muramasa  10/10
Red - Hard vocab, advanced (but 'proper') sentences, some technical (dry) parts. You can read this before red, but don't bother if you're just going to whitenoise past sentences you don't understand. It's philosophical fiction. Go for 100% comprehension or read something else.

Astelight 7/10
Red - Both the vocab and grammar are about as hard as it gets. The only 救い is that the topics discussed in it remain fairly non-abstract for the most part and even maintain an impressive lack of schizo-ness, given the presentation.