Photoshop. The Color Replacement tool changes the color to gray (instead of white). Saturation/transparency problem?

Question

Working with color

There is an image:
File format: JPEG | Color Depth: 24

I'm using Adobe Photoshop CC (2015.5.1) . I need to change the background color from gray to white [ #FFFFFF / RGB(255, 255, 255)]
First I used the Magic Wand tool . I separated the background and filled it with white using the Paint Bucket tool .
Selection:

Fill result:

Looks sloppy. The hair is cut off. The transition from hair to background is sharp. This is not what I wanted.
Then I switched to the Color Replacement tool . Using the Eyedropper I selected the background color and set the replacement color to white:

But the tool changes the background color to gray (instead of white). This "white color" seems to be transparent and unsaturated. It's not white. I will show how the color is replaced using the example of blue (since the replacement of gray with gray is not noticeable).
Assigned colors:

Result:

Instead of blue, some transparent, desaturated blue is obtained.
Question: How to change the background color normally. The first method does not work correctly. The second method changes the color better (without cutting the edges of the hair), but the colors are kind of transparent. How can I change the background color to pure white?
Update:
Question was answered here (in English): Photoshop's color replacement tool changes to gray...

Answer 1

In order for the Color Replacement tool to work with full saturation, set the Saturation slider to 100%
Well, in fact, you need to look at the lessons on the Cut-out tag, for example. Learn to create neat masks.