Instead of changing the Colour Balance, you could also use the Colour Replacement tool. That way, you wouldn't necessarily need the lasso tool, but it helps. They both acheive the same basic effect, but I think it would be easier to get the colour you want with Colour Replacement.
I agree. Another useful way to achieve such a thing is with the brush selecting from the properties Color/Hue/ Color burn. It is really useful. Note you should have it semi-transparent or less, so as to manage tones.
Another way to do it would be to use the Lasso tool as suggested, but instead of color balance, do image > adjustments > photo filter, and choose the color. This works for sepia on b&w photos too. Thanks!!!
A great basic tutorial. Another good way of recolouring bits is to play with an adjustment layer, as then you get to paint in exactly where you would like the colour to go to without marking the original picture layer (it's a good way to do things esp. if you need to go back and change).