I mean, it's magic, but there's not much more to say about it.
If you read the source code you'd probably go, "wow", but this description remains unimpressive.
You can reskin the pots using Content Patcher and targeting:
aedenthorn.ConnectedGardenPots/sprite_sheet
Just make sure you understand how the sprite sheet is laid out. The original sprite sheet is in the mod's assets folder.
Works with Watering Can Tweaks and doesn't interfere with Wall Planters.
Technical
Requires SMAPI, uses Harmony.
Compatible with Mod Updater for automatic updates.
Code is at https://github.com/aedenthorn/StardewValleyMods.
If you want to complain or ask for help or help me test my mods, you can visit my Discord server.
A list of all my mods for Stardew Valley is available at https://www.nexusmods.com/stardewvalley/articles/895.