Instructions
Open the photo into a new layer in your editing program.
Use the "Lasso" tool to select the portion of the picture you want to colorize.
Add a new layer and fill the layer with the color of your choice using the paint bucket fill tool. Change the opacity of the new layer so you can see the old photograph underneath and the color is just a light overlay.
Continue adding layers for each area of the photo you wish to colorize, changing the layer opacity to the same color as the previous layer to have the same brightness of color.