Step 5 and Step 6 are different options. You may follow Step 5 if you want a single dominating color or you may skip it and follow Step 6 for multiple blending colors. You may also try both, one after the other.
Step 5: Now, to change your hair with solid color, press Ctrl B to open up the color balance pop-up window.
This time it is your turn to experiment with these colors, just move the sliders to change the color. You may also change the color of the shadows, midtones or highlights by clicking the radio button under tone balance. Make sure that Preserve Luminosity is checked. After clicking OK, press Ctrl D to deselect selection in order to view the effects clearly.
If you don’t like your chosen color, use the Ctrl Alt Z which is the undo multiple previous actions. Press it twice to bring back the selection and to undo color change. Then, you may try another solid color or proceed to step 6.
Step 6: Make sure that the hair is still selected. Now we need to click the fill icon at the icons tray and choose the Gradient Tool as shown below.
At the top of the screen, click the arrow of the gradient color to bring down more selections. Choose a color combination. You may also select from different gradient color sets as highlighted below. Change the mode to Overlay and decrease the opacity to 35-80%.You may later undo and change the opacity if the color is too light or too strong.

Now point your cursor at the top of the photo and then drag it all the way down across your hair.

As mentioned in Step 5, you can always undo your previous actions using Ctrl Alt Z to try another blend.
Changing your hair to solid color is a helpful way to see how you look like especially if you are planning to dye your hair.