Okay, so after some digging, Tolkien never described skin tone about dwarves in the books. At least none that I found. It’s stated that he based them off of Norse mythology.
Digging into that, there isn’t that much in depth information about Norse dwarves appearance, and that they range from having a formless, glowing appearance, to looking like humans, and there is actually a reference to a race called dökkálfar (elves that are typically identified as dwarves) as “blacker than pitch.”
It would seem that Tolkien, the actual source, wasn’t concerned about skin tone of the dwarves, and the movies just happened to use an all white cast.
I also came across this page:
https://tolkiengateway.net/wiki/Blacklocks which has this passage about one of the original 7 father’s houses:
2021: The Lord of the Rings Online:
The House corresponding to the Blacklocks is called the Temámir. Dark-skinned with raven-black hair, they are considered the wisest of the Seven Houses.
It’s not like this show is the first time to have non white dwarves.