To go on a hybrid.
I'm using 35mm Bluemels with 35c kojacs, on my Boardman- they're pretty tyrehuggy, if I'd had a bit more space in the frame I might have gone up a size just to make some room, but they do work fine.
You would probably be best with 45mm guards. You can probably use 42mm.
It depends on how true to size the tyres are, and what other tyres you might want to use.
Sks P45's
Take all the sizes with a pinch of salt.
I run 35/37c marathon plus // SKS 35mm // tortec velocity race
The mudguard are rated upto 32c MAX, the rack is rated to 28c tyre, yet both fit very snuggly and never rub despite the tyre being far larger than the max spec
Sks P45's
That's what I use with 35c Marathon Sports
I've got SKS Bluemels 42mm. My 35mm Kenda Small Block 8 is an excellent fit. My "35mm" Schwalbe Marathon Mondial, that actually comes up 37mm, is a bit tight and I get some minor spray off the tyres in really wet conditions.