Here’s a tutorial that I’ve been dying to make. Well-constructed two-color pieces are beautiful, economical and the hallmark of an expert designer. [Note: These techniques can also be used to create 3, 5 and 6-color documents, hexachrome seps, screenprinting seps, and more.]

Here is a small sampling of 2-color works. Each beautiful (and copyrighted!) image in the collage was printed using 2 inks. [edit. OK, just noticed the 3-color Blue Note cover, so sue me. Same principle. :P]
Standard four-color printing uses the 4 process colors: cyan, magenta, yellow and black. The short reason for this is because the subtractive primaries are cyan, magenta and yellow (not blue, red and yellow as we’re taught in grade school). Pigments in most inks are weak and impure, however– especially cyan– so we use a fourth ink to boost the color gamut. Turns out black helps the most, as CMY alone produce weak shadows. Thus your basic desktop printer has 4 inks: CMYK.But on a giant printing press, we can use any inks we like, in any combination. Lithographic printing presses are monstrous devices, operated by skilled pressmen. It matters not to either what colors are used to run a job. All sorts of neat effects are possible, simply by expanding on boring old CMYK. Special ink colors are called Spot Colors. There are formulas for mixing these and systems for classifying them. The most universal system is Pantone, which includes super-cool metallic and florescent colors. You can buy color guides with all the Pantone colors printed on coated, matte and uncoated stocks. These guides include formulas for mixing any of these colors from 11 base inks, and they even let you know which of these colors can be reproduced with CMYK.So why use spot colors? Lots of reasons; here are a few:

Finally, 2-color comics look AWESOME, which is also the reason I’m so interested in this.

First things first, pick your 2 colors. You’ll most likely want to use black and some other color. This gives you a range from white to black, plus your spot color and all its tints and tones. (image) Now you’ve got to construct everything in the job with just these 2 colors. First is QuarkXpress: go to edit>colors, and click “new”. Under “model”, select PANTONE Solid Coated (or metallic, pastel, uncoated…whatever applies). Then pick your color from the chart or type it in the field. Hit “save”, and you’re done. This icon should be next to the color in the color palette (image), meaning it’s a spot color. Now you can use your spot color in boxes, rules, and text. You can even colorize grayscale TIFFS by selecting “picture color” from the color palette. How nifty! (These things apply to InDesign too, just do some cursory research.) Just be sure to use only the spot color and black in your design (duh!).Next is Illustrator. Make sure your document is in CMYK color mode. Now open the swatch palette, and delete all the swatches except registration and “none”. Now, click the arrow for the swatch options, and go to “open swatch library”. You’ll see a huge list of every spot color system under the sun; pick the same Pantone one you did in quark. (They MUST be the same: coated, uncoated or otherwise!) A new palette will open up; just find your color and click on it. It should now appear in the normal swatches palette. Next, create a swatch with the following values: C=0%,M=0%,Y=0%,K=100%. This will be your black. Done! Just work as normal, using ONLY your color and the special blank ink swatch. To create tints, click on either swatch and select a tint from the color palette’s “tint ramp”. You can save out as a plain vanilla .eps– nothing special to do there.

And now, Photoshop. As I mentioned earlier, you can tint a grayscale image in Quark. You can do something similar-yet-cooler in PS, first by converting to grayscale, then to “Duotone” mode. A duotone is a raster image composed of 2 inks. What we did in Quark was a 1 ink monotone; in photoshop you can make monotones, duotones, tritones and quadtones with 1, 2, 3 and 4 inks, respectively. So convert to duotone mode, and you’ll see a window with some options. Process black is the default first ink- click on the second color to set your spot. Click on “color libraries”, and select your Pantone color model (you must be getting used to this by now!) Select your spot color, or type the number in really really fast. Now click on the curve boxes to adjust the ink levels for each color. Fine-tune to your own taste, and work light– black plus anything is pretty dark. PS includes a whole bunch of samples, just click on “load”, pick one, and change the spot color to your own. Save out as a Photoshop eps.

The image above is a duotone composed of 2 inks: black, and Pantone 2985

If you’re really bright, you’ve figured out that duotones, cool as they are, don’t give you maximum control. For that, you need to become a true Graphic Design ninja. Enter the Multichannel DCS 2.0. When you convert a duotone to multichannel mode, your single “duotone” channel will split into two separate proper channels, one for each color. You can then paint, select and otherwise manipulate each channel as if it were a layer. That’s right, you work directly in each channel. Layers aren’t even an option in multichannel mode, so do your heavy-duty editing first, before it all gets flattened and rasterized. Then play around with total control over where both inks go. Liberation at last!

The black ink is removed from the cup above. As you can see, this allows us total freedom to manipulate duotones.

For non-duotone images, there are a couple more steps to get to multichannel mode. When you change most images to multichannel, you get three channels: cyan, magenta and yellow. You’ll need to double-click on each channel, and then convert two of them to your own colors. (Of course, delete the third channel.) If you’re experienced with channel blending techniques, this allows for greater control; otherwise, stick with the duotone-to-multichannel conversion.

And back to Quark, for one final test. If you’ve followed along, your job should separate as two plates, and there shouldn’t be any CMY nonsense in there. Here’s how to test: Bring up the print dialogue box in quark, and under the “Layout” tab, check the “separations” box. (Make sure you’re printing to a PDF or PS file, not a physical printer. If you try printing to your inkjet, it won’t work. Your printer doesn’t mix Pantone inks, although that would be really cool.) Now click on the “Output” tab. There you’ll see every color that will be separated and output. There should be Process Black and one spot color, and NOTHING ELSE. If there is, go ahead and print the PDF. You’ll get separate pages for each color, so you can go to the cyan, magenta and/or yellow pages to pinpoint the offending culprit. If not, you’re all set! Let the output service bureau handle screen angles; they’ll know what’s best.

Congratulations! You’re an official 2-color expert!