The photo is blue under the camera light, Pentax kr, how to adjust it?

Background blur requires three conditions, 1. Large aperture. 2. telephoto. 3. Close to the subject and far from the background. The more the three conditions are met, the better the blurring will be.

18-55 can only use 55 ends, and the maximum aperture can only be 5.6, as close as possible to the subject. However, 55 focal length +5.6 aperture, no matter how hard you try, blur is limited. You can take a close-up small still life, and it is basically impossible to take a portrait unless you take a close-up face.

On the contrary, it is also true to blur the subject and have a clear background. With a large aperture, the camera is closer to the subject and focuses farther.

It is suggested to supplement the knowledge of "depth of field" and understand the principle clearly, so you will naturally know how to control where the blur is.