Yes, we know that globalization is the key to success. I'm not talking about revenue here -- I'm talking about colors in Illustrator. More specifically, I'm talking about how you create your swatches in your documents.
For solid colors, there are really four different "kinds" of colors that you can work with.
1. The Ghost Swatch - By far, the most "dangerous" to use in Illustrator. However, in my experience, this is what people use most often. I'm referring here to the ability in Illustrator to apply a color to an object in your file directly from the Color palette. Without defining or creating a swatch for that color. Not only is it difficult to now make changes to that object's color later in the workflow, it is also nearly impossible for prepress folks -- or anyone else for that matter -- to find that color unless they know exactly what they are looking for. The problem is that using colors in this way is so darn convenient (we're human after all). It would be nice if Illustrator had a command that would create swatches from all colors used in a file, and it's a feature request I hear often. Hopefully it will appear in Illustrator one day.
2. The Process Color Swatch - Probably the next most-often used kind of swatch, the process color swatch is simply a way to "memorize" the values for a particular color. If you think back to the days of doing those paint by number projects (for me that would be, oh, two days ago?), you can imagine process color swatches as those little plastic containers of paint. There's one for yellow, one for red, blue, etc. Each time you want to use a color, you just dip your brush into that color and bam, your object becomes that color.
3. The Spot Color Swatch - Next on the list are spot colors -- and spot colors are "special" for two reasons. First, they are special because they create a separate plate when you print color separations (necessary for many different printing and production needs). But there's another reason why spot colors are different. When you color an object with a spot color, an invisible link is established between the swatch, and the object itself. That means if you ever modify the swatch itself, any objects in your document that use that color will update as well. This is not the case with process color swatches. If you apply a process color swatch to an object and then later update the swatch itself, the objects will not update. As an added bonus, a spot color can also have a tint value specified. That means you can apply the color at different strengths.
4. The Global Process Color Swatch - Finally, there are global process color swatches -- which aren't used often enough these days. A global process color swatch is a combination of the process color swatch and the spot color swatch. Global process colors separate to process plates, but they ACT like spot colors in that object retain links to the swatches (so updating the swatch DOES update the artwork on your artboard), and you have the ability to specify tint values of those process colors as well.
In the image above, you'll see three yellow swatches. The one on the left is a process color swatch, the middle one is a global process color swatch (with the telltale white triangle at the lower right of the thumbnail), and the one on the right is a spot color (with the dot in the white triangle).
When defining your swatches, be sure to check the box marked "Global" in order to get the benefits of working with global process color swatches (above), including the abilty to specify tint values (below).
In reality, I see little reason for not making global process colors as the default setting for Illustrator. Just about every other major graphics application known to man (Quark, InDesign, FreeHand, CorelDRAW, etc.) treat all colors as global process colors. But in any case, hopefully this will paint a sweeter picture for you the next time you create some swatch colors for your next illustration or design.