Answer 1

RGB notation is basically a mix of base colors with different saturation of each:
https://www.sololearn.com/learn/HTML/1036/?ref=app

You can use a color picker to get more intuition on it:
https://www.w3schools.com/colors/colors_rgb.asp

Or a bunch of color-themed codes on SL, I particularly like this one:
https://code.sololearn.com/W6uvMQgGaQcW/?ref=app