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I have all the mechanical pencils in the Pilot Color Eno line. They're 0.7, though... but anyway, they're all good! I don't have a problem with breakage, and the colors are nice. Not the brightest ever, but that's what pens are for anyway.
I've had a purple Color Eno for about 6-7 years now, and am very satisfied with it. Just recently got the other colors as well.
I recently picked up all of the Color Eno line as well for color coding my Scripture highlighting. They are softer leads than what you may be used to, but so far only the yellow has had any issues for me. I underline key phrases and on that bright white, thin, paper Bibles are printed with, a single line of yellow is just too hard to spot.
The leads can break, I am pretty heavy handed though. It took me all of about three breaks to just advance less lead and I have had no problems since. I can recommend them but as stated above, they are .7 mm leads.
If you don't mind buying new pencils, then I like the Color Eno pencils themselves. Some people think they are not the best quality, but mine are extremely comfortable in my hand and the grip is downright non-slip in my fat little fingers. I caught myself wishing the other day that they made a black Color Eno in .5 mm, because I could slip in some Uni-Ball leads and make it my main pencil quite easily, I like them so much.
Best of luck and I hope that helps!