Have you given consideration to the colour of your clock hands? A colour will stand out against wood no matter what, but (for example) gold hands on oak will mostly disappear. I would think it would make an easier to read clock if you did the full sternum & ribs in the same colour with a darker underlayer, and top layer slightly smaller - so you get a raised shadow look, but don’t have to worry about the clock hands blending too well with only a part of the design.
I’m glad you like it, I just came up with it on a whim! As for the clock hands I really didn’t give it much thought. However, I was thinking of doing the clock face (background) in maple or cherry and the ribs/sternum in birch. Maybe doing the hands in black?
Having said that, What size overall should I make the background with the clock face? I’ve never made a clock before and am not sure how large to make that, or the ribs/sternum. Also, how big do I make the hole for the clock assembly?