The classic MCS is pretty unmistakable. More than 2 colors, usually white, blue, orange, sometimes red, sometimes with yellow and/or green or both . . . The preferred type is what used to be known as a "Miller" swirl; some have argued that the less swirly ones (usually with yellow, green, blue) should not be called MCS, not being very swirly. Still not entirely sure where I come down on that, but I do keep mine separately.