This way lets you specify the exact colour and vary the background colour, should you wish. It uses a masked Solid Color layer.
1. Open the grayscale image
2. Cmd/Ctrl-click the gray thumbnail in Channels panel to make a selection of luminosity
3. Press Shift+Cmd/Ctrl-i to invert selection4. Mode > CMYK
5. Add Solid Color layer - blue
6. Add Solid Color layer - white
7. Put white layer below blue layer
To add to Conroy's excellent post, do you intend to print on a press? Does it really need to be in CYMK?
I prefer to create logos in RGB, (with a CYMK preview, View>Proof Colors - CTRL(PC)/CMD(Mac)+Y) so that it can be used on a website, or in an application...
Good point, Pierre. I considered mentioning that, too.
Thanks so much for your clear explanation. You realy helped me out! I hope this tread will be helpfull for others in the future.
I wondered if it would be possible to make the background transparant, but then I found out that I could just delete the white layer
You guy's are Brilliant!