As stated above, I would also recommend the usage of HSV color space. Try to experiment on the generated channels and choose the one which works best for your images; (H,S, or V).
Contrast enhancement is proven to be useful in the context of edge detection. Quantisation, humm, I am not sure to be honest.
p.s. In your original post, you talked about color image segmentation, but now you are after skeletnisation, which are two distinct topics in my eyes :)
In my opinion, the first one you must identify the type of your image.
In further, maybe you can try to mix-and-match RGB and HSV color space. I have combined the Red channel and Saturation channel to segment the blood microscopic image. I also have tried the LAB color space, but it is not suitable for my dataset