Let's all admit that we used a Hex color code chart.
But I hope that you won't need one anymore after this tutorial.
Hex Color codes are composed of 6 digits. Divide them by 2 and you'll get 3 sections. This 3 Sections are Red(#ff0000, Green(#00ff00) and Blue(0000ff). (RGB) These are the primary colors that mix up to create the desired color. As you notice, the hex color code of each color has 2 F's on a single section which is why it is a solid color. (Let's say Solid colors are colors without the mix of any colors from outside sections)
# (ff)- Section 1, (00)- Section 2, (00)- Section 3 (this is #ff0000)
Now, let's talk about Light and Darkness.
Darkness isn't a color but a state where there is less or the absence of visible light. That's why pure black is #000000 while as pure white is #ffffff
Now, let's use Red for an example. Red's Hex color code is #ff0000. Since we're going to make it lighter, we'll add a 1 equally on the other outside sections which would become #ff1010. You could use either side. #ff1010 and #ff0101 are the same.
The hierarchy of the intensity digits (from lowest to highest) is: 0123456789ABCDEF
That's why black is composed of 0's and white is composed of F's.