Can anyone help me out in understanding RGB model to apply on code I.e hexa decimals

Tell us what’s happening:

Your code so far

<style>
  body {
    background-color: black;
  }
</style>

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.186 Safari/537.36.

Link to the challenge:
https://www.freecodecamp.org/challenges/use-hex-code-for-specific-colors