why is it that red and green are the x-mas' primary colors....why not other colors instead?

Answer 1

From http://www.christmaslore.com/the_true_meaning_behind_the_christmas_colors.html

GREEN: Celebrate Life

Green signifies life. You probably remember this from high school biology class. Plants depend on chlorophyll for life. With respect to Christmas, green symbolizes the hope for eternal life that Jesus offers. There are so many ways that we now incorporate Christmas colors, green in particular, into our Christmas celebrations. Evergreen trees are green and are commonly associated with Christmas as are many Christmas lights, Christmas ornaments and bows.

[Edit: Christmas has connections to a pagan winter solstice celebration important to the first Christian converts that celebrated the rebirth of the sun and of life in late December when the days began getting longer again in anticipation of spring. Green, as in trees and grass, symbolizes this life and rebirth cycle.]

RED: Celebrate the Sacrifice

The color red also has deep origins too. Red is intended to symbolize the blood of Jesus. At Christmas time, we see red everywhere. Santa sports red with his popular costume. Most Christmas decorations contain some red too.

The combination of the Christmas colors red and green are also part of annual Christmas celebrations. Holly, which consists of green leaves and red berries, is meant to incorporate both red and green to symbolize life and blood.

Red became more popularly associated with Santa when Coca Cola company began an advertising campaign in the early part of the last century and Santa was sporting a red outfit, which very clearly matches the red of this popular beverage’s cans.

Answer 2

Red and green for Christmas were adopted when the Roman church moved the feast day when Christ was born from Spring (or late Winter) to align with the Solstice. The church adopted the red and green, the evergreen tree, holly, mistletoe, and etc etc etc to keep folks from celebrating the Solstice and replace it with the birth of Jesus. White and blue (the colors of the Blessed Virgin) are also appropriate colors for Christmas, and the altar cloths are often white for a feast day.

Answer 3

Those were the colors of the blankets that the baby Jesus was wrapped in when he was found by Ma and Pa Kent when he arrived from the planet Krypton.

Answer 4

When you are in head over heals with some one in your life, the probable advices you would get would be 'Stop' or 'Proceed'. The two advices would represent red and green.
Do you still have doubts?

Answer 5

well it is in my opinion because green is the colour of new life and energy, also the christmas tree, it spreads enthusiasm all around

red simply bcuz it is the color of celebration, enjoyment and pleasure