Replacing colours -- Photoshop 7

I'm currently making an icon and on one layer, I filled certain parts with red but now I've changed my mind and want to make those parts orange. I don't really want to have to go and re-select those parts again so I was wondering if there was any way I could have Photoshop (I have 7.0) select all the red parts for me and replace it with the orange I want. I was thinking maybe it's possible with the eyedropper tool but I'm not sure.