Closely relates to MC-241321. It likely also relates to MC-197123.
The bug
The red oval displayed around the screen when the player is close to or past the world border is only present in the Fancy and Fabulous! graphics settings.
According to this 2014 post on Twitter by Dinnerbone, the fast graphics option is only intended to change the transparency of leaves as well as rain particles, neither of which are relevant to the presence of this effect.
How to reproduce
Use Fancy/Fabulous! graphics
Approach the world border
Note the redness around the edge of the screen
Now switch to Fast
Notice there is no longer any such redness
Expected results
In line with Dinnerbone's comment, this red effect would still be present even in Fast graphics.
Actual results
The effect is absent entirely.
Linked issues
Attachments
Comments 7
This is certaintly not intended:
https://twitter.com/Dinnerbone/status/527075906595340288
"The fast/fancy graphics button now only controls leaves transparency and rain particles."
The world border warning effect is most certainly not a leaves block or rain particle.
Intended.
While not an authoratiative source, the MC Wiki states that the warning tint is "only visible on Fancy graphics".