Step 1. Original image.
To find nice grapes photo you may search Google Images or use this one (click the photo to get it full-sized - 1797x2700).
Step 2. Grape shape.
Pen tool is absolutely necessary for making both simple and complicated selections in Photoshop. We will use it to select grapes to be colored.
Press p to activate Pen tool and position the pointer where you want to begin grape outline. Click to define the first anchor point, then click or drag to set other anchor points. If you make a mistake, use Ctrl-Z to undo one action or Ctrl-Alt-Z to undo several actions.
Step 3. Making selection from the shape.
When you have finished creating the shape, turn off shape layer visibility in the Layer Palette. Then Ctrl+click on the shape layer icon (it's yellow on the screenshot) to make selection. Make "Background" layer containing grape photo active.
Step 4. Adjust Hue/Saturation.
To change color of the selected grape you can use quick and easy or more advanced technique. To change color quickly, press Ctrl+U, then adjust Hue and Saturation (check Colorize). Don't Alter Brightness too much, as it will make grape look too unnatural.
Step 5. Advanced technique: Adjustment Layers.
More advanced, but little more complicated technique is using adjustment layers. When the grape is selected, use Layer - New Adjustment Layer - Hue/Saturation menu. Click OK to create layer when prompted, then adjust color.
Using adjustment layers is non-destructive, as it doesn't Alter color of the original image. You can also change color of the grape at any time by double-clicking adjustment layer icon. You may ask: "Ok. I have 34 adjustment layers. How can I find the one that I need?" Good question. Simple way to select the layer you need is:
- Press v to activate Move tool
- Turn on Auto Select Layer in the tool settings (see the upper part of the window)
- Click on the grape. Adjustment layer above it will be automatically selected.
The result.
More Tutorials: 
