i am using same ad placement and format except colors are different and i notice that a web which have low traffic get higher CTR + CPM why its so different?
It's all down to psychology. Obviously the colours cause visitors to percieve your website differently and thus act differently. You're colour scheme may give users a more calm feel (usually pale colours - pastel blue, green, orange), and so they might stay for a longer period of time, increasing the chance that they will want to navigate the site.
I had an ebook a while ago that had a lot of stats on CTR and color and there was a great variation in CTR based on color. The best seemed to be close to a white background with dark blue letters that looks quite like the blue letters of a visitied link. Color scheme does play a significant role in click through.
i think the reason may be your site category (in my expreinece , site category effect the ctr . for example forums does not get good ctr)