Holly Golightly calls them the "mean reds". Blanche Devereaux calls them "magenta." They're not "the blues", though they're in the same family.
It's being worried without having anything specific to settle the worry on because there's just too much to worry about. It's feeling neglected and abandoned and completely sorry for yourself while yelling at yourself that you are too old, mature and independent to feel neglected and abandoned and completely sorry for yourself. It's wanting to sleep to get your head quiet, but not wanting to sleep the day away because time is always so short. It's a teeth-aching, numbing anxiety with no solution in sight because the problems are so non-existent yet so ever-present and giant because they are your mental creations--your brain gone completely wild--to the point that you need to speak in second person in order to put the words in the right order.
It's knowing that you have something to do, a lot to do, but can't do any of it. It's wanting to curl up and forget that there is a world out there, yet screaming, "Don't ignore me, world, don't you love me? Don't you care?"
The nice thing about the "colors" is that because they are so intense, they wear out easier than, well, sensibility and normalcy. They simply can't sustain forever, and thank God. And because you are old enough to know better, you also have an arsenal of techniques prepared to deal with the "colors" when they descend upon you. You clean the house. You rearrange the furniture. You watch Sex and the City until you've seen Carrie through Big and Aiden and Big and a 20-something and Big and that guy from Office Space and Big and Barishnakof and Big. You do yoga. You eat popcorn and have a drink and a smoke to take the edge off. And you wait for the "Colors" to get good and tired and fall asleep in the corner.