Try the Commands Troubleshooting and Help page if you get stuff with server errors.
Minecraft Version Notes
1.13 Java minecraft give command
Banner color ids change as part of the The Flattening.
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Added: Chess pieces
Added: Cute Banners
Patch: Fixed alpha transparencies on banner previews.
Added: Banner Generator
Patch: Top Triangle Sawtooth was swapped with Top Triangle
Added: Letters A-Z
Added: Numbers 0-9
Added: 22 initial flags
Added: Banner converter