Answer 1

https://stackoverflow.com/questions/22239803/how-does-hexadecimal-color-work

Answer 2

https://www.sololearn.com/Discuss/618590/?ref=app

Answer 3

Hexadecimal values go from 0 to F: 0123456789ABCDEF, They start with a hashtag #. and they could be a set of 3 values or 6: #00F is equivalent to #0000FF.
RGBA values contain numbers from 0 to 255 with the alpha parameter that is a number between 0.0 (fully transparent) and 1.0 (fully opaque). example : rgba(255, 0, 0, 0.3) /*red with opacity*/

Answer 4

If you want to get these values from a webpage on your browser, you can install an extension like colorzilla that will allow you to do so

Answer 5

You have also online converter if you want