Go back to your main image and create a new layer at the bottom of the layer stack and fill it with white. (CMD/ CTRL+A, Shift+F5, and then select white). Then create a new layer above this, paste your sketch onto it and position and scale to make it fit correctly.
Now duplicate the top layer of the girl and turn this level to a grayscale. You are going to have to give the face a suntanned complexion to help the contrast work with the strong background so use the layer effects and choose the overlay option. Again, adjust the opacity to get the feel you want.
Now merge your hand-drawn elements and go to Image > Adjustment > Hue And Saturation and adjust the colours until you are happy. Duplicate the layer and then do the same, getting a colour that contrasts with the other perfectly. Then go to Layer > Layer Mask and hide areas of the top image to allow the first colour to show through.