Since these are apps that ship with the client by default, I think they should have matching U.I. For example, Explore has a (nice) dark theme and People has a light theme. Chat is somewhere in between, since it appears to have a black background but a lot of the larger fields are white. Personally, I prefer dark themes. In general, I think pure whites should not be used for interfaces-- very light grey would be my white equivalent. I'm not a very visual person though so don't take my word for it.
Since these are apps that ship with the client by default, I think they should have matching U.I. For example, Explore has a (nice) dark theme and People has a light theme. Chat is somewhere in between, since it appears to have a black background but a lot of the larger fields are white. Personally, I prefer dark themes. In general, I think pure whites should not be used for interfaces-- very light grey would be my white equivalent. I'm not a very visual person though so don't take my word for it.