Hexadecimal is a base 16 number system, which means there are 16 characters, ranging from 0 to F. That means, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A (10), B (11), C (12), D (13), E (14), F (15).
You start by counting from 0 to F. These are your first digits. The next digit comes in a form like “10”. In hexadecimal, “10” refers to 16 in decimal. And so on, until 1F - 31. The next form comes in 20, as 32, and so on. The maximum for two characters is 9F. The next is 100, and so goes: 10F, 1F0, 1FF.
The easiest way to implement hexadecimal with redstone is with signal strength. The power indicates the current number.
You can face at a redstone dust and hit F3 to open the advanced details menu in the game. Then, look at the right side, and find the property “power”, which should be the signal strength. It ranges from 0 to 15, and always shows in a decimal format. This is, the easiest, fastest, and most popular way to implement hexadecimal with redstone, although obviously there are several other ways to implement that.
In most cases, hexadecimal numbers will also have a prefix with 0x. For example, if you see someone writing 0x20, you know it for a fact it is hexadecimal and actually refers to 32 in decimal. You can also add a suffix with the lowercase letter ‘h’, like 20h, which you know for a fact, is 32 in decimal, but I suggest adding a prefix 0x instead. Nobody understands nor uses the suffix h in these days, and it may be often confused with something else (e.g. hours).
I hope you learned something. Have a nice day!