Question

1 .which tool replace the existing colour in an image with the foreground colour ?
please tell correctly ​

Answer 1

Background Swatch sampling option

The Background Swatch sampling option will replace the Background color with the Foreground color.

Answer 2

Answer:

As you drag the Color Replacement Tool over your image, Photoshop continuously samples the color that's directly under the crosshair in the center of the cursor. This is the color that will be replaced, and it will be replaced with your current Foreground color.