In this representation, each meson consists of one quark and one antiquark shown as intersecting circles within the larger circle. | |
The colors of each quark represent a property physicists call color. The quarks aren't really colored, but it is a convenient way to represent the property. Quarks can be red, blue, or green while antiquarks can be cyan, yellow, or magenta. | |
The one quark and one antiquark in a meson must have colors that combine to make white. Only the anticolor of a color combines to make white. Red's anticolor is cyan; blue's anticolor is is yellow; green's anticolor is magenta. The part of the two circles that overlaps represents the mixture of the colors of the two quarks. |