For many images, the color of the lighting can have an effect on the color of your image, and perhaps will create a "color cast" that will negatively affect the "color balance" of the image and leave it looking a little drab. Photoshop gives you many options to improve the color of your image. In this image on the right, the colors look pretty good, but the light illuminating this image was blue (because it was the blue sky) and there is a slight blue color cast to it.
One of the first easy ways to improve color is with photoshop's auto color feature (Enhance>Auto Color). Try this and see what happens. If nothing much happens, then you know you'll need to try something else.
Remove Color Cast
Next try Remove color Cast (Enhance>Color>Remove Color Cast). This is a handy feature which allows you to use a grey object in your image to help photoshop "calibrate" the color balance of the image. This gives you some control of the subjectivity of color balance and so you can easily have many variations of improved color balance.
Improving the saturation of an image can often help you get a better idea about its color cast and the colors that are in the image...try to add Saturation, but be careful not to overdue it.
There is another feature which allows you to have variations on color balance, and this is the "Variations" feature...try (Enhance>Color>Variations). With variations, you can easily get a sense of the various color options you have and more intuitively decide which color you like best. Keep in mind that you can control the courseness of the changes.
Enhance>Adjust Color>Adjust Hue and Saturation
You can adjust the saturation of the colors in your image with photoshop. The Saturation of your image is a description of how rich, (or pure) the colors in your image are. This is often a helpful effect if your original lacks good separation between colors, or the colors are very muted.
Channel Specific Levels
A bit more complex, but powerful way to adjust a "color cast" is to use the levels feature in photoshop, which can also be used to improve contrast and "lighting". (Enhance>Adjust Lighting>Levels).