find the same colour in one image

Hello,

do the people know if you can find matching colours in one image? as in i find a colour with certain RGB dimensions, can i find the same or 'roughly' the same colour and whereabouts the same colours are, in the same image. the problem is im trying to paint a picture and i want to know which colours are the same so it correspsonds almost exactly when complete (its quite a fiddly picture so correct colours are essential)

thanks very much and if i confused anyone then thats somethin i suppose

ahh ive worked it out eventually, my bad for wasting no ones time x