Bay leaf is yellow
Thank you for your question about your bay plant. Your plant appears to be in a pot; I'm hoping it has good drainage, since over watering a plant will cause root rot and lead to (almost) certain death. The most likely cause is a nutrient deficiency, especially nitrogen, which can be rectified by adding complete fertilizer. Finally, there may be an insect infestation, which will require you to look closely under leaves and on the plant trunk and stems. Here is a link to an article about these three possibilities. Here is another article with care suggestions, that you might find helpful.
Hope you are able to solve the problem(s)!