Update colours for k0S project icon

For the most part the logos look good, but there is some inconsistency in the colour logos. The `color icon` set have a white top half, where the rest of the colour logos have a black top half:

_Originally posted by @nate-double-u in https://github.com/cncf/artwork/pull/580#pullrequestreview-3089858633_

Compare the k0S project icon's `color icon` set with the other colour logos, using the screenshot and the discussion in pull request #580 as context. Locate the relevant artwork files and update the inconsistent top-half colour; done means the colour icon matches the other colour logos.

Written by the indexing model from the issue text.