It's coming from the stump of an unknown camellia. It was hard pruned two years ago and is the only limb with this coloring. Is it harmful?
Variegation due to virus. It will come and go. Seldom important.
The virus that causes this type of variegation is generally not harmful to your plants. It causes foliage variegation like the one in your image and flower variegation. If a plant's flower would normally be solid red, one that has been infected with the virus would have red flowers with some white blotching. Variegation can be spread by grafting, and in the camellia world, more times than not, it was spread purposely. I would not worry about it at all. Your plant looks very healthy.
The effect looks pretty on the leaves though. Reminds me of some tropicals plants.
I have virus infected camellias and true variegation on a few camellias as well. This looks like variegation. It's mainly on 1 side of the stem. Try to encourage growth from the variegated side and propagate from that. This variety has a consistent variegation quite different from the viruses I see on Camellias. Of course only a lab test tells for sure.