Hi! Some months ago I read a manga but now I can't find it anymore. I've searched pretty much everywhere - MU, my manga lists, Google, etc - but I really can't seem to find it.

It was a shounen-ai or yaoi (I can't tell which genre because I only read the first 3 or 4 chapters and the story was still building at that point). I can't remember if it was a manga, manhwa or manhua. The first chapter was full color, if I'm not mistaken, but then it turned to the classic black and white style. The main character was a black-haired male student (I'm not sure if he wore glasses but I think he did ?). He was the classic small, cute and shy boy you can find in shounen-ai and yaoi manga. One day a new student with orange hair got introduced to the class and he sat near the MC. He was pretty popular since the beginning because he was handsome and cool around people. The MC and the new student came to feel a little attraction for each other. An unpleasant female rival got introduced between the 2nd and the 4th chapter. I think that she had cram school or something similar with one of the two boys (?).
The style was really cute and the colors used in the full color pages were all pastel (like this).
I read it on a site like Lehzin were you need coins to unlock the chapters.

This is all I can remember. I really hope that someone can help me 😢

That summer (KIM Hyun) seems closest to your description but it has a lot of differences, like it's completely coloured, the female lead isn't annoying and she's the MC, not the black haired dude...so I think it isn't the right one.
These three are a lil less similar
Unriped expression
Curse note
School life (Soonbo)
Maybe you read it on foxtoon, comico or Naver. Try going through their lists. I hope that helps 🙂

I finally found it! I saw the picture of the cover BY CHANCE while surfing the net, but I recognized it right away! The manga is He, him & Us. It's a bit different from my memories but I'm sure this is the manga I was looking for! 😀

Oh, I would've never known....but glad you found it 🙂