Incorrect color escaping on pattern match exhaustivity warning

[OlivierBlanvillain]

/home/olivier/workspace/dotty/tests/patmat/t7466.scala-- [E029] Pattern Match Exhaustivity Warning: /home/olivier/workspace/dotty/tests/patmat/t7466.scala:8:4 
8 |    (b1, b2) match {
  |    ^^^^^^^^
  |match may not be exhaustive.
  |
  |It would fail on pattern case: (31mtrue0m, 31mtrue0m), (31mtrue0m, 31mfalse0m), (31mfalse0m, 31mtrue0m), (3
1mfalse0m, 31mfalse0m), (_, 31mtrue0m), (_, 31mfalse0m)