Lately, I been reading quite some more manwha cause of their good stories. But I can't help but notice that manwha use a lot more colored pages, sometimes even fully colored volumes. Or just all pages color, why are color pages more commonly used in manwha then manga? Is there a specific reason for this?
There's the so called WebToon, which is most likely the one you refer to (and you are reading). Frankly speaking, printed color pages are not cheap. They cost a lot more than B&W page and are difficult to print correctly. With webtoons there's no such thing as "printing", everything is done digitally.
Manwha that is done in B&W completely due its distribution method (printed) which you will not see color pages (like Chevalier of the Absis, or ID which has some color pages as bonus), there's also webtoons that could be printed later on (like The Breaker/NW) and there are those that are not printed (almost all webtoons).
Is difficult to see a Manwha (or any printed media) in full color. The only case I know of is To Love る which is released later on after the black and white pages are released.
Is a matter of cost of distribution of the media, which is cheap for webtoons so artist can offer color pages.
In the example you gave, "Magician" by Kim Sarae, this is an original webtoon that is published using Naver.
- A list of manwha that are in full color (MU): ~250 titles
- All kind of manwha (full color and B&W) (MU): ~1500 titles
There are lots of black and white Manwha, just that are more difficult to find since they are distributed physically.
Actually, most manhwa aren't colored either. Along with some webtoons, only a few manhwa are colored.
The reason they aren't colored is because it takes a long time to create manga and manhwa, and it's a lot more expensive if each page is colored. Most of the creators start working alone without any financial support, thus making colored pages very difficult. Western comics are mostly made by large companies like DC or Marvel, and these companies have enough resources to make colored comics quickly.
If you'd like to confirm that manhwa is usually black and white, MyAnimeList has a list of manhwas for reference.
MyOtakuWay explains the difference between manga and manwa.
Searching for manga on MyAnimeList.net will let you see that most have just one author, not a campany or a staff.
Finally, ComicList is a list of comics where you can see that they are made by a company.
Long time ago before when there was no internet yet in this world, I always found Chinese comics (maybe weekly comics because they were thin) in full colour. I don't know why, but probably it's because of tradition.
In contrast, manga have no colours probably because of the Japanese mentality - they don't like to waste money etc. I'm saying this because, in national universities, even the copy paper there uses recycle papers. Not to mention the shounen magazines etc, that one's quality of paper is terrible, that's why they can sell a thick shounen magazines considerably cheap.