We are left with following problem, upon which TcT provides the
certificate YES(?,O(n^1)).

Strict Trs:
  { w(r(x)) -> r(w(x))
  , b(w(x)) -> w(b(x))
  , b(r(x)) -> r(b(x)) }
Obligation:
  runtime complexity
Answer:
  YES(?,O(n^1))

The problem is match-bounded by 1. The enriched problem is
compatible with the following automaton.
{ w_0(2) -> 1
, w_1(2) -> 4
, r_0(2) -> 2
, r_1(4) -> 1
, r_1(4) -> 4
, r_1(5) -> 3
, r_1(5) -> 5
, b_0(2) -> 3
, b_1(2) -> 5 }

Hurray, we answered YES(?,O(n^1))