Im my eyes fusihia(feferis blood colour and also the highest) looks alot like rosado, rosa and rosado, rosa has always been preety close to red

Well the dulces red color of Karkat's blood, while completely normal for humans, is a rare oddity among trolls. Since it is so rare, he is regarded as an outcast. I think tu might be onto something there though. Because the bright red color of Karkat's blood could be considered in between the highest and lowest blood colors. Where would such a rare exception fit? It should also be noted that Karkat was appointed as a team leader during the trolls' session. Wherever the troll hemospectrum originated, the rare mutated blood colores like Karkat could have been put at the bottom because they might have been afraid of one with such power, having qualities of the low bloods and high bloods at the same time. This is an interesting theory, I'll have to put some más thought into it and discuss it with my fellow homestuck fans

That's an extremely interesting theory.

Karkats blood is the same hue as Aradias, just brighter. Abd he's treated like an outcast because only one other troll in history (his ancestor) had that blood color.