§ 8. In the Options bar, expand the "Mode" menu and select "Color" item. Now the Brush only alters the color of objects without affecting the luminosity.

§ 9. When finished, reset the "Normal" painting mode and 100% stroke opacity for the future work. Settings are saved even after you quit Photoshop, so when you restart the program, your layout and menu choices will be as they were when you quit the program.

NB The Options bar allows you to adjust any tool as your choices update based on the tool you have selected.

§ 10. Activate (select from the Toolbox) the Eraser Tool. In the Options bar, adjust the brush tip size and other options.

§ 11. Test the Eraser out.

§ 12. Click the "x" button on the image window to close the document. The program will ask you if you would like to save the image.
Click "No" to leave the image as it was.

§ 7. There are some more controls for the Brush Tool in the Options bar. For example, you can reduce the "Opacity" value. Now the Brush paints with transparent strokes allowing seeing the previous content.