I've been using these colour changers for 4 years now and they've always been very quiet, in the 5mm variety. I've tried 3mm and 10mm ones and they were very noise, unusable even, but the 5mm ones were always nice and quiet. So nice and quiet that I stopped checking my bags of them to make sure they were staying nice and quiet. I recently got a bag of 500 though and they're noisy, I confirmed it myself with my amp although I couldn't hear the noise under my usual testing circumstances...I needed the full gain of the distortion channel to bring out the noise.
I believe about 50 or 75 of these noisy LEDs went out in miniberators over the last month, from serial # 75ish to #150ish, all in the red finish. And Pete's proto, 'cause I popped one in there for him.. Tommy's mini too... I'm sorry dudes!

It's not a noise everybody will hear, it depends on your rig and how your gear is set up and how much gain and/or compression and/or volume is involved.
If you find that you can hear the noise though, just shoot me an email (ryan@drscientist.ca) and we'll make plans to pop in a solid red LED for you. I'm going to only use solid colour LEDs for awhile now until I can be sure I've got a silent batch again.. hopefully anyway, I'm worried now that that's the end of the colour changers in our pedals.
If anybody would like a handful of colour change LEDs for fun, not audio purposes, let me know and I'll mail you a package of them. I've got a big bag of them here that I can't use but they still look cool as heck.
Sorry for the complacency with the noisy ones though, I should have checked better that they were quiet. *smacks forehead*