Consider the TRS R consisting of the rewrite rules

1: w(r(x)) -> r(w(x))
2: b(r(x)) -> r(b(x))
3: b(w(x)) -> w(b(x))

There are 4 dependency pairs:

4: W(r(x)) -> W(x)
5: B(r(x)) -> B(x)
6: B(w(x)) -> W(b(x))
7: B(w(x)) -> B(x)

The approximated dependency graph contains 2 SCCs:
{4}
and {5,7}.

- Consider the SCC {4}.
There are no usable rules.
By taking the polynomial interpretation
[r](x) = [W](x) = x + 1,
rule 4
is strictly decreasing.

- Consider the SCC {5,7}.
There are no usable rules.
By taking the polynomial interpretation
[B](x) = [r](x) = [w](x) = x + 1,
the rules in {5,7}
are strictly decreasing.

Hence the TRS is terminating.