exactly the colors in my imagination when i hear these words - Indian summer
and i always was in bewilderment, why they use the word "INDIAN"
Is it about the India or the Indian ppl inhabiting North America.

So here the explanation :

"J. M. Flowers of Carpentersville, Ill., provided the following interesting explanation that predates 1778. He writes, “My wife and I were vacationing in Scotland and we overheard a Scott mention Indian Summer. I asked how the term started in Scotland. He said it had to do with sending British troops to India in the late fall. The weather was still warm in India — thus the term “Indian Summer.”"
by: Tom Skilling.
https://wgntv.com/weather/weather-blog/how-did-the-term-indian-summer-originate/