There is nothing wrong with red hair. Japanese are not simply used to the color. There are fewer reds than blonds and brunettes anyway, and that's one of the reasons why it is admired in US. In a sense, you might say Japanese are still live in the time of Anne Of Green Gables when it comes to hair color. But I am sure they will catch up soon. Meanwhile, do not take it personal. Nobody is forcing you to waok in Japan, so you have the choice of take it or leave it.
Outside of dramas(Japanese predominantly) I have never seen any asian person with red hair. In India, lots of women use henna for their hair as they are supposed to be good for hair . Over a period of time especially when their hair becomes gray, application of henna leaves the hair with a bright orange color.