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Japanese also most maga are black and whit and Korean manhwa with colours
Manhua is Chinese same with colours

Manga is hand drawn while Manhwa is digitally drawn.

Country of origin primarily

Manga refers to Japanese comics (many are drawn in black & white due to the maturity and customs of the publishing industry). While they were traditionally hand drawn (which played a big part of being black & white), many modern manga are now drawn using digital tools either fully or partially (this is in part due to the lack of jobs that can afford to pay assistants since piracy has hurt income streams)

Manhua refers to Chinese Comics. Due to when the publishing industry focused on exporting its comics like the US & Japan, most are digitally colored

Manhwa refers to Korean Comics. Like Chinese manhua, except due to South Korea's status as an official ally of the USA, has been able to benefit from US publishing practices to give themselves a competitive edge (which plays a small part in why Manhwa is generally seen as better in comparison to manhua)

For anyone curious enough to want a detailed understanding of why manga is still black and white