Colored/Tinted/Pastel Images
Keywords: photoshop, colorize, add color, coloring photos, Change to black and white, grayscale, greyscale, tinting, removing, desaturation, desaturated, withe, noir et blanc, tons de gris, enlever la couleur.

Option 1. From a color image
This version will keep all the original colors (there is yellow/orange/red on the flower)

1. Make a duplicate layer (>Layer>Duplicate Layer...)
2. Change the background layer to B&W.

3. Erase the areas you want to be seen as B&W. Remember to zoom in for the detailed areas.
Instead of erasing you could also create a Layer Mask OR Extract The image.

4. Change the Opacity (?) of your colored layer for the desired effect.

Option 2. From a Black & White Image

1. Change to image to Color Mode (>Image>Mode>RGB Color)
2. Create a new layer.
3. Paint over the areas you want to be colored (Create new layer for each color)
5. Switch the top layer mode to "color" and change the Opacity to taste.

Option 3. From a Black & White Image

1. Change to image to Color Mode (>Image>Mode>RGB Color)
2. Create a new layer.
3. Apply a Gradient Map Adjustment Layer and Mask the right areas. (Create new Adjustment Layer for each new color).