Q.Why are my hibiscus leaves purple?
Each leaf is half purple and half green with the exception of new growth. How do I help it?

Certified GKH Gardening Expert
Although it can be hard to tell without seeing the issue, there are a few things to cause this.
If this is an irregular pattern, and not a clean line established between colors, then you may be looking at a phosphorus deficiency, or a soil that may be a little too acidic. You can amend with dolomitic lime, and some phosphorus and potassium heavy nutrients.
If this is a clean line of separation, and it is happening somewhat predictably, then you may have a chimera! This is a case, simply put, where two different organism fuse, and become one individual with portions of genetics and traits from each contributed individual.
Should this be the case, then there is nothing to be done.
Here is an article that will help you to grow these plants: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm