I'm looking for a shrub for the middle of the lawn to replace a young
Japanese Maple that a late frost killed.

The ideal would:
(1) Be suitable for the borderline of Zones 6 and 7.
(2) Be as colorful as possible for as lomg as possible.
(3) Full sun location with good drainage.
(4) As hearty as reasonably possible in regards to disease/insects and
water needs.
(5) Full height at maturity of at least 4 feet with no upper limit on
height.

Your ideas would be greatly appreciated.