Basically, yes see herePhotoshop - I think
select Layers then New Adjustment Layer and then Hue/Saturation
when the box appears turn the saturation fully down -100
you now should have a total B&W pic
you need to let the colour be seen from the Background layer below
select the brush tool and pic a brush and adjust its diameter to suit the size of the item you want to have in colour.... make sure the opacity is set to 100%
Now just go over the bit of the pic you want in colour and left click....
the brush tool will now remove the part of the B&W layer you have the brush on.
if you make a mistake just click the B&W box to reverse the colours and the when you hold down the left button you can put back the B&W with your brush.
Obviously you have to start with a colour image