Pieris floribunda does not have the brightly colored new growth - that's P. japonica and the hybrids (some, not all). And it is only marginally hardy in zone 4. Smokebush is not hardy at all in zone 4 and needs sun to maintain any dark coloring. About the only thing I can think of that might work are perennials rather than shrubs - Actaea racemosa (used to be Cimicifuga) 'Brunette' or 'Black Negligee' or Ligularia 'Britt Marie Crawford'. These offer pretty dark (not exactly red) foliage and are very happy in shade. And all manner of dark leaved heucheras could work but these are small and many also "green" out in much shade.

Dark colored - red or purple - foliage in shade is not at all common and even less so with shrubs. And the limitations of your zone kind of decrease any possible selection further.

You might consider ninebark (physocarpus), reportedly winter hardy in your zone. Some varieties have reddish/purplish leaf coloration. I have seen 'Diabolo' hold the purplish color in dappled shade. 'Coppertina' has a brighter color, but I have no experience with how well it holds that color in shady conditions.

Here is a link that might be useful: Missour Botanical Garden: Physocarpus