4. Create a new layer under the line drawing layer. Use the Paint [Bucket Tool] in the selected is segment.
5. Push [Ctrl+D], deselect, and fill the space with [the Pencil Tool].
6. [Image > Adjustments > Hue/Saturation].
7. Check Colorize, turn up Lightness and change other than black. Adjust the Hue, Saturation and Lightness as you like. After doing so, you have finished.