It's mostly just text on Wikipedia so Midnight Lizard uses "Simplified" mode there by default to preserve resources but not colors. If you need more accurate processing please switch to "Complex" processing mode. You can switch modes on the "Common" tab and then press "Apply".

Unfortunately Firefox has a bug that does not allow to upload exported color schemes.
If you don't like to use built-in sync then you can try to do it manually:
1) Go to about:debugging#/runtime/this-firefox
2) Find Midnight Lizard and press Inspect
2) Paste into the Console "chrome.storage.sync.get(null,x=>console.log(JSON.stringify(x)))" without quotes and press Enter
3) Copy results from the Console to the file.
4) Open about:debugging#/runtime/this-firefox on your another device
4) Paste into the Console "chrome.storage.sync.set(JSON.parse('replace it with the text from the file and keep single quotes'))" without quotes and press Enter

PS: if you have disabled "Sync settings across your devices" in Midnight Lizard settings then you need to use "chrome.storage.local" instead of "chrome.storage.sync"