I see no real problems. The puckering is probably due to a common non-lethal leaf disease that just makes them look ugly for the rest of the season. The leaves usually don't even die, although there may be some dead angular areas. This problem occurs in cool weather in spring (although usually not as cool as that!).

The purpling I see as a good sign. If the leaves actually froze, they would be black and limp or crispy by now. The color is a common reaction to cold produced by many plants, and usually will turn back to more green with warmer weather. Since your lilacs are still young, I think they should put on some healthy new growth, too.

Rick

Whew! That is good news. I thought we were close enough to the big lake to escape this frost. Surprise!
Thanks, Rick.

I was just thinking, and just to make sure: did anyone do any spraying for weeds nearby? That could cause puckering too.

Today, the puckering seems to be going away. Most of the purple leaves are still soft and normal appearing. A few are drying out and starting to fall off. All but one plant seem to have lots of green left. Luckily, I bought three extra plants as "spares" in case I do lose any in the hedge row.