Q.My Redbud Trunk Is Turning Red From The Ground Up
What Is it and what should I do

Certified GKH Gardening Expert
Is that an older tree? If so, the orangish layer underneath will often start to show through and is not a cause for alarm. However, the bark on your tree is sloughing off, which could be natural due to its age or could be due to disease, so keep an eye out for any additional symptoms like yellowing leaves or branch dieback.
Also, all those plants beneath the tree are competing with the tree for water and nutrients as well as preventing oxygen from getting to the tree's feeder roots. The best thing you can put under a tree is mulch out to the dripline.
https://www.uky.edu/hort/Eastern-Redbud
https://hort.extension.wisc.edu/articles/eastern-redbud-cercis-canadensis/
https://www.gardeningknowhow.com/ornamental/trees/tgen/peeling-bark-on-trees.htm