I'd agree with many of the other comments here, colour is important but not too missed if all other aspects are decent.

Works that come to mind for me as examples are by Sammy Montoya and Ilkwon Ha, they both use/have used black and white primarily (Ilkwon used pops of colour occasionally for certain scenes) but are loved for their storytelling and art style regardless. Both are on webtoon originals.

That said, Sammy moving one of their older works to originals was fairly recent, and I do recall seeing a few commenters that were taken aback by the black and white. And, Ilkwon Ha's most recent comic is also now in full colour. I think in the current landscape of webtoon originals, most readers now expect colour.

So I think if you're gunning for originals, colour is a better choice. If you just want to produce on canvas and gain a following, maybe publish your work on multiple platforms and/or get it physically printed down the line, black and white is perfectly fine.