(final edited photo below: 3 Tangerines, oil, 9" x 12")
So, you've tried the Levels and maybe the Hue/Saturation tricks, but your image is still not quite there: maybe you've got a decidely 'cool' or 'warm' cast that is not present in the actual artwork. This is where Color Balance can be of use. I tend to use this one near the end of the editing process, as it seems more subtle to me. This is the tool for when your values are right, your contrast is correct, but the color is just a little off.
The image below has been edited for contrast and levels already; it does have a bit of a 'milky' look in real life, but the red of that tablecloth is off.
To open the color Balance dialog box, click Cntrl+B (Cmnd+B for Mac users, or Image/Adjustments/Color Balance in the top toolbar). As in previous tips, I've used a 'control' image duplicate on the left so you can see the change.
Starting with the Midtones, move the sliders to add more color as needed; like many of the Photoshop tools, you will need to trust your eyes and experiment. It's also very handy to have the artwork right where you can see it as you make these adjustments.
In this case I could see that the tablecloth photo had too much purple (blue) in it, and needed to be more red. (I had painted it with a warm red earth, Blockx Capucine Yellow Deep.) The sliders were moved toward red and yellow, respectively.
In a separate step, I adjusted the 'highlight' colors, again choosing to move toward red and yellow, but also a bit toward green. (Another mini tip: For each adjustment you make, copy the previous layer and adjust on the new layer. Then if you really get lost, you can back up).
As a final step, I adjusted the Shadows, this time moving toward Magenta and Blue. This step was more logical than intuitive; shadows are often cooler shades. This is so close to original painting, I've amazed even myself.