I've been struggling with how to separate colors in Photoshop CS3 for the purposes of silk-screening. I've finally got it down, using "spot colors."
Here are some tips, with a video I found that explains it visually:
- Make sure you set your image type as CMYK
- Use "Select->Color Range" to create a marquee around the colors you want to print in the same color. Hold the shift key down when using this feature to select multiple colors at the same time. The preview will show you in white what is selected.
- Once you have the color regions you want selected, copy (Cmd-C).
- Look for your layers window. There should be a tab also called "channels." Select it. There should be a little tiny arrow near the top of that small channels/layer window, clicking it should bring up a list of functions, choose "Create new spot channel"
- You should be prompted with a dialog to select the color for that channel.
- Viola! Repeat for each color.
- You can click the "eye" for the CMYK channel, and you'll see the layer you've created.
- When you have two channels "eyed" you'll see the composite colors. When you have only one, you'll see the channel in black-and-white, where black will be the ink color you've designated upon printing.
- Print using color management options of "separations." This will print each color on a a separate page.
- Throwing in registration marks will also be helpful for alignment when it comes to screening.