I have a graphic in photoshop that is red, it's two hands that are bent to make a heart. The graphic is red and a single graphic. Is it possible to change it that the right hand color is different from the left hand color? For example, can I change it the right hand to be blue and the left hand to be green?
What I would do is use the marquee selection tool and select the part of the graphic you want to recolor. Once it is inside the marquee selection tool's selection - right click inside the area and click 'layer Via copy'. You now should have that part of the graphic on a new layer. Now right click on that new layer and click blending options > color overlay. Here you can change the color.
That's how I do it. I copy it instead of cutting, in case I make a mistake and want to get rid of it. Also because cutting usually leaves a bit of a gap between the two new layers.
The easiest way to do this is to select the red so there are "marching ants" around it, then select the blue color, then the paint brush and start painting the hand you want to be blue. The selection will keep the color within bounds. Then select green and color the other hand to be green, and decide how you want the color to interact if the hands touch anywhere.
You can add a layer on top of layer with the hands, with color blending mode. With the lasso tool (or any selection tool) select the area where you want to change the color and fill it with the color you want.
To make sure it does not mess with the background by clicking in between both layers while holding alt/option. This way you can also select a wider area than only your hand, which is time saving.