Design coloured, bold, italic Minecraft sign or book text — then copy the /give command straight into your world. You can't type colour codes directly on a sign in survival, so this is how everyone with pretty shop signs and lore books does it.
A sign is a wooden block you can write four short lines of text on. Place one on any wall, floor or fencepost, right-click to type, and everyone in the world can read whatever you wrote. Perfect for labelling chests, marking a hidden door, pointing the way to spawn, or leaving a note for a friend.
The catch: when you write a sign the normal way, Minecraft only lets you put plain black text (or white on dark signs). You can't type in colour, you can't make text bold, and you can't do italic. Which is a shame — coloured signs are one of the classic looks in Minecraft builds.
The way around this is a command: /give. You give yourself a sign that's already got the coloured, bold or italic text baked into it. When you place it, the text appears in the colour you picked. The tool above builds that command for you — you don't need to know any coding.
Doesn't work on servers where you're not the owner (they usually block cheats). On Realms, the owner has to switch on cheats first.