There is a reason for that.
I would strongly recommend painting the block in light colors. Some day you are likely to have an oil leak. I couldn't imagine trying to find the source of an oil leak on a black case. This is an area where maintainability should come before cosemetics. no one see's it anyways. Lyc's are well known for sprouting small leaks and seepage.
I painted mine light blue and this has helped me find two small leaks that were identified by tracing the very light oil marks across the block. Red should work just as well.
Larry