Why didn't the northern Asians develop blonde hair or different colored eyes?

Different reasons. Blue eyes were caused by a genetic mutation, which occurred 6,000 to 10,000 years ago near the Black Sea. This has been proven and there has been a lot of articles written about it. Skin color change takes many generations to occur (like thirty generations). But you need the conditions necessary to make this happen. Northern Europe and Northern Asia, while both cold, do not experience the same number of sunny days. Northern Europe is heavily cloud covered. But time in an environment is important also. Europeans have been in Europe for tens of thousands of years. Fossil evidence of Cro-Magnon man has proven this. The question remains, how long have Asians lived in Northern Asia. Probably not for tens of thousands of years.

Because similar people are derived from similar places. It is been postulated that the eye color blue was derived from a mutation in northern Europe(a very recent one, WAY after leaving Africa). Now according to biology, two different species (in this case sub-species) will converge if they share the same way of life (overall niche) - That's why you have Eurasians (places near the middle east). ALSO, recent discovery from max planck institute - Neanderthal genome was found in small amounts (1-4%) in Europeans and Asians - a little twist to the coming out of Africa theory. Hope I have helped. If not, I hope someone else will.

The large variety in eye color and hair color, the normal occurence of freckles, and the ability to blush, all traits normally found among northern europeans. Is believed by some to be due to a mutation, others believe it is due to interbreeding with homo neanderthalensis, both of these thesis's would explain the great variety in the gene pool among northern europeans.

The travelers of the Bering Land Bridge were not caucasoids but mongoloids. There is some legitimate speculation that caucasoid people with lite eye colour migrated in smaller numbers via northern europe around the ice into north america...1000's of years ago. Eye colour is a fairly recent change. One might likewise ask why haven't Europeans developed more brown eyes since the ice age has ended... One could simply regard the lite hair and lite eye colour as a caucasoid trait... along with big noses... Europeans didn't develop lite eyes as they moved north, but after they had moved north and in areas isolated from contact with other groups...long enough to develop certain traits but not long enough to become a distinct species.

Blue and gray and green eyes and blonde red and light brown hair coloring are linked to recessive genes in humans. Many Africna and Asian cultures regard this coloring and other forms of albinism as "demonic" or a mark of haivng "barbarian" ancestry so people with such coloring are less likely to pass on the recessives. However despite this cultural bias even in Mongolia the occassional individual with green or blue eyes and hair thats dark brown rather black or even red heads are born. I've read people with green eyes are occassionally born amidst the (H)mong people and they're NOW SE Asian tho their oral traditions claim they migrated from further north. As for Asian groups further north the mutated genes don't seem to have reached that far yet. Partial albinism in Amerind populations may be responsible for reports of "white" Indians from the 16th to 19th century. Yes Asians will have to wait longer.

two reasons: the climate is warmer in asia than in europe asians also come from africa but they moved from their natal lands later than the ones who moved to europe( asia is a lot farther from africa than europe) and europeans had more time to adapt to the new weather conditions