it depends on the red and blue color scheme or hot and cold ie red (fire) blue (water), gold (has ho-oh Fire), silver has (lugia water), ruby( volcano groudon) sapphire(water kyogre), diamond ( are created with immense heat and pressure even though color is blue), pearl( are found in the ocean, color is pink a derivative of red), then White( white is considered a warm color ), and black( the absence of color associated with cold dark places).
the order for Red>Gold>Ruby>Diamond>White>White 2>Y
and Blue>Silver>Sapphire>pearl>Black>Black 2>X
and yes in japan it was red and green, green is a calm color, X's legendary comes from a forest he is calm
.