The bug
If multiple translucent particles coincide when using the Fabulous! graphics setting, they appear to combine to form a brighter texture than otherwise.
How to reproduce
Create a repeating command block executing the following:
particle block light_blue_stained_glass ~ ~4 ~ 0 0 0 0 1000
Build a room made of bright looking blocks around the fountain of particles
Compare visuals for Fancy and Fabulous! graphics
Thank you for your report!
We're tracking this issue in MC-217515, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki