Below might only repro if there is a colorscheme used that has rainbow brackets non-default. I'll update with something that should probably work everywhere.
julia> str = Base.AnnotatedString{String}("foo [endz] bar", [(5:5, :face, :julia_rainbow_bracket_1), (10:10, :face, :julia_rainbow_bracket_1)]);
1.13:

1.14:
Potentially #60212 which would suggest JuliaLang/StyledStrings.jl@9bb8ffd but this is purely guess work.