Not a major bug at all but I'll report it all the same
MC-257351
Coloured blocks tab uses the American spelling despite using English (UK)
Resolved
Invalid
0
Thank you for your report!
However, this issue is Invalid.
Translations for languages other than "English (US)" are done by the community and take place on the Crowdin Minecraft Translation Project.
Please use Crowdin for suggesting and adding translations.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki