This far north, there is nothing evergreen that has true purple foliage year-round.

Loropetalum might be worth looking into, but they can become small trees. Not always hardy in northern 7a though. ZhuZhao Fuschia is the hardiest of the Loros. There are more dwarf varieties like Ever Red®, but they are not as hardy from my trials. Worth a try in a protected spot though?

That said, there are a number of good hardy evergreen shrubs that offer reddish NEW growth. Eventually it turns green but they are worth considering. I'm thinking of Pieris 'Katsura' or 'Mountain Fire'. 'Flaming Silver' has variegated leaves as well as reddish new growth. Stunning when it first flushes out.

Here's my Katsura ↓

Flaming Silver ↓

Some Ternstroemias and hollies have reddish new growth.

Also, not a shrub, but Heuchera has many reddish to purple colored varieties. Probably not evergreen in your zone though? Still, it holds leaves well into winter probably. Great for a mounding effect! Can be a bit difficult. Likes part shade and really good drainage. I've seen them do well in an Eastern exposure in Virginia. This one below is called 'Forever Purple'. I just got some for my front yard. It's amazing in color.

Beautiful!