You can't tell that she's red headed, the tone of grayscale doesn't reveal that. Ruby also has been shown to not have any magic talent, specifically in a previous chapter she asks Black Crow if she can use magic to they can activate the teleporter. Alchemists also haven't been shown to have...
This series is a manga original and has no LN
Also only found out just now the artist makes like a ton of Hentai so it makes sense why's there's so much fan service
I think the treasurer (Mimasaka) is the same character as the author's previous one shot: https://mangadex.org/title/80283172-d0be-4009-bbfa-6931e2af5544/barairo-no-hishatai
The chapter definitely seemed pretty poorly translated originally, in that nothing really made sense. Typesetting wasn't bad which I think people notice most easily, but if your translation skill is weak I would advise against translating yourself.