The idea for a distinctive canadian flag started in the 1920's, but wasn't implemented fully and accepted by the monarchy until Pearsons governments of the 60's. It went through many design stages, even at one point having 3 maple leafs instead of the one.
As for the colours, the quote below I found on a canadian government web page, here is the link it has a complete list of facts about our Flag.
www.pch.gc.ca/progs/cpsc-ccsp/sc-cs/df3_e.cfm
"Dr. Stanley's design is based on a strong sense of Canadian history. The combination of red, white and red first appeared in the General Service Medal issued by Queen Victoria. Red and white were subsequently proclaimed Canada's national colours by King George V in 1921."