Q.planting under a patio
I have a concrete patio. I want to cut a couple of holes in the concrete and plant some color. First hole cut, excavated hole 14″ x 12″ x 24″ deep. Planned to fill with good compost/planting mix then plant the color. Now the problem: The material removed is damp clay and I’m thinking that these holes may eventually fill with water, be unable to drain and the plants will drown.

Certified GKH Gardening Expert
You are probably correct, especially because the clay soil is probably compacted because it's been under a patio.
These articles have some suggestions:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/yard-drainage-problems.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/yard-drainage-problems.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/how-to-improve-clay-soil.htm
You could also consider plants that don't mind a poorly drained environment. However, you'll also need to make sure these plants don't dry out too much on hot days.
https://www.gardeningknowhow.com/ornamental/water-plants/wgen/water-tolerant-plants.htm