According to PK on ESPN: http://espn.go.com/blog/afcsouth/post/_/id/48260/colts-have-spent-31353333-cap-dollars
This includes contracts for Butler and Moala. Also says we gained $1.158MM by releasing Zibs.
He's estimating they have $13MM +/- left, not including what they need to allocate for draft picks.
Maybe releasing Zibs is a precursor to signing another FA.
The $13MM should give Grigs just enough to sign that 6th string CB from Cleveland or the 3rd string tackle from Oakland that he has his eye on...
One can only hope