How to shoot the silver part of jewelry? My camera is Canon EOS450d. How to adjust to the best state?

The lighting effect of the first picture is still good.

Did you read it? The colors of your two photos are different, so the problem is still the white balance. Take a picture with manual white balance and have a look. Adjust it slowly, and the color temperature will change when the light passes through the diffuser.

Finally, pay attention to the lighting angle to get the necessary reflection and avoid unnecessary reflection.