I have had a camellia bush for about 25 years. It still flowers every year, but the color is not as true as it once was. It's almost faded. I don't have the name of the variety any more. It is solid dark pink in color. I do fertilize every year.
Camellias Lack of Color
Certified GKH Gardening Expert
This article may also help: https://www.gardeningknowhow.com/plant-problems/environmental/fixing-color-faded-flowers.htm
Anonymous, you fertilize, but what analysis and how often. I would suggest a well balanced (10-10-10 for example) fertilizer and use it according to package directions. The following link is to an article on camellia problems: https://www.gardeningknowhow.com/ornamental/flowers/camellia/identifying-and-fixing-problems-with-camellias.htm
There is a search window at the beginning and end of the article. If you enter the word camellia, many more links to articles, several of them Q&A, will appear.