The best is the 12550 hood from Leica, made for the Elmar-M. It allows you to use the standard Leica lens caps and does not intrude in the finder.
Usually the Color Skopar comes with a small hood, more a ring, that gives some protection. However, then you'll need the original aluminium CV lens cap, not very nice.
Of course you can use all the other lens Leica hoods for 50mm and 35mm f/2 lenses too, but these are big, clumsy and expensive.
I have the LH2 hood, but I've never used it in all the sixteen years that I have this lens.
Erik.