Belonging of the rings:

The thumb of the right hand: "zero" (零, rei); wore Pain. Its color is violet-gray.
The index finger of the right hand: "blue", "green" (青, ao, sho); wore Deidara. Its color is turquoise.
The middle finger of the right hand: "white" (白, shiro); wore Conan. Its color is white.
Unnamed finger of the right hand: "cinnabar", "scarlet" (朱, shu); wore Itachi Uchiha. Its color is red.
The little finger of the right hand: "sign of the wild boar" (亥, gai); wore Zetsu. Its color is green.
The little finger of the left hand: "sky", "emptiness" (空, ku); wore Orochimaru. Its color is blue.
Nameless finger of the left hand: "south" (南, nan); wore Biwa Jūzō (only in anime), and later Kisame Hoshigaki. Its color is yellow.
The middle finger of the left hand: "north" (北, hoku); wore Kakuza. Its color is dark green.
The index finger of the left hand: "three" (三, San); wore Hidan. Its color is orange.
The thumb of the left hand: "pearl", "sphere", and also, the black king in shogi (玉, gyoku); wore Sasori, and later Tobi. Its color is purple.