How is it that there are people with red , yellow ; black and with skin color ?

Because babies come in all of those colours plus... erm... camouflage.

yellow can be a region from where you are from but it can be a disorder like jondus( i dont know how to spell it) or too much veggies not enough iron, red i think if you are white you may turn red from pigment, i dont think i understand the question, sorry lol, but i do know i am white and sometimes i get red lol

people have different skin colour due to where they originated all to do with the environment

try going back to the fall of the tower of Babylon