Ok guys, here's my secret, but don't tell anyone else....lol
There is always more than one way to skin a cat in PS, but I find this way is the easiest, especially when colouring a large area. Open your photo, copy the background to a layer. SHIFT Q changes it to quickmask mode. Select a brush, I usually choose a smaller one for edges and with a steady hand outline the area you want to colour. Select a larger brush and fill it in. You can go around the outside with the eraser and rub out any red that you don't want. SHIFT Q will select the outside of the area you have just coloured, so just desaturate, under Image/Adjustments. Flatten and save. Easy peasy lemon squeezy. Hope that all makes sense.