Is that 'Col' as in 'Colon' or as in 'Colonel'? Let's hope it's just 'Column' or simply the latin 'col'.  ;)

Apart from the wealth of associations, I agree that it'd look nice.

Guess it really is just me with the 'Co' antipathy...

Maybe you're right Shai. Any particular ideas?

Yet another go:

[#1:] Trying the old 'dotted C' shtick since any big fat 'C' almost screams for a little something in the middle, I ended up with something that with goodwill may even give a faint association to 'Co' (and to a button of some kind?) and I kinda like it. I used a 90 degree gap in the 'C', so it's very geometric which I like. Might that be something to work from?

One idea would be to make the middle of the dot darker again to promote the 'o' association even further, but the resolution can't support that and I think it'd get messy fast. How fat the middle dot should be is a good question but I think that it should have some weight.

It's been tried before with severely limited success. The actual key size on a 72 dpi screen is 54 pixels wide, which is a fair bit more than the 16 pixels we're discussing here. On the small icon I fear it'd become cramped and too stylized to convey the idea properly.

Also, keys with something on them may be a bit overdone already - even if nothing would fit better thematically in this case.

I like better the dot in C version, although I'm not sure it's quite there yet.

Tomlu, thanks - and I agree: Looks nice, but it doesn't say 'Co' too clearly. The problem is that if it does, I find it hard to maintain graphical power.

Shai: Any suggestions then? Anything more fancy with the colors? Making the dot bigger? Or something else entirely?

I like the concept of #7, although I think it could easily be seen as a number "6" or a ying-yang logo as well.
Could you make a non (or less) bold version of it?  I think it will then suffer less from these problems.

Haha! Well, the Belgian lottery logo does remind me of the Yin-Yang... Belgians are almost as crazy as us Norwegians. (Bet you'll be insulted by the 'almost'.)  ;)

You're right: The squiggle does look a lot like a number 6. Better do something about that.

[#4-6:] I started fiddling with the yin-yang associations, and decided to use the Golden Ratio rather heavily. What do you think?
The first looks a bit like a machined tool part I think. Very geometric.
The second one may be my current favourite. Reminds me of Aubrey Beardsley and Art Noveau, with asymmetric swings. Still squiggly, but I like it.
The third one is a less geometric 'C', and maybe the clearest one when it comes to separating 'C' from 'o'?

I'm still experimenting, and trying to let impressions sink in.

#7: I went even further with the 'Art Noveau' one. The risk with that is that the 'C' and 'o' part aren't clearly distinct, and the thin lines may get too thin for a 16x16 design; if I were making it for higher resolutions the contrast between the thinnest and thickest lines would be even more dramatic I think. I'm still intrigued by the graphical qualities of it, but maybe the #6-type is safer after all. Unless...

#8: A separating line makes the point clearer, but maybe it loses a bit of the elegance and the bottom arm of the 'C' now seems to flow into nowhere? I made the bottom part even thicker now that it has that separator - maybe that's interesting. Not sure it works in the tray though. [Looking at it, there are interesting associations to be made:  "Yellow Submarine" slash "Jefferson Airplane" slash "Aubrey Beardsley"....]

#9: Keeping the ball rolling on the more symmetric #6-version, I made the letters even more font-like. Looks nice in the tray. The top dot on the 'C' didn't take well to being as narrow as the lower one, but the symmetry should be sufficient nevertheless.

Ooo, this is intrigueing!

The 'Art Noveau' design is brave, fun and artistic but may be too much of a stretch? And it probably looks better in larger sizes than at 16*16 pixels.  :(

The 'font' one works very well in the tray, and wins the vote of the (two, so far) people. I'd like to hear even more opinions. Shai?

Come to think of it, the 'font' design still looks a bit like a steampunky tool of sorts. "Colemak - a powerful addition to your lifehacking toolbox!"  ;D

[Update: I've used both these icons in different Windows trays for nearly a week now. Both are nice, and I think I love them equally by now. Still fishing for opinions, in other words!]