It is not required reading, nor necessary to understand, in order to use the Creator or qplanner.
Hexadecimal colours
Images on electronic screens are generally displayed using Red, Green, and Blue components.
Historically each of these would range from 0 to 255. Where 0 is none of the colour, and 255 is the strongest it can be.
Using these 3 colours, at differing values, you can create virtually every colour.
This is technique is called additive colour mixing.
For example, if you set Red to 255, Green to 240, and Blue to 0, you'll end up with a nice yellow:
Similarly, Red: 22, Green: 196, and Blue: 233 makes a lovely blue:
You might write this colour like so 22,196,233.
By using Hexadecimal (Base 16) we can make the colour more compact, and uniform.
In hexadecimal colours range from 00 to FF, and it means our lovely blue can be stored as #16c4e9, and the yellow as #fff000.
The # just helps the computer know it should be a hexadecimal colour.
There's no need to worry about converting colours manually.
Most digital art tools, and colour related websites, will display the colour in hexadecimal for you, making it easy to copy/paste in to other software.
And the creator has a built-in colour wheel, so you can causally pick a nice colour if you don't already have one lined up.