How to select and change a color in photoshop using eyedropper tool:
To select out the different colors, create a new layer and go to Select - Color Range. Click on the color you want to sample with the regular eyedropper tool. You can play with the fuzziness to get more of an accurate selection. Also, if you need to add or take away from your selection, you can use the eyedroppers with the plus and minus symbols next to them to do so.

Next, go to Layer - New Adjustment Layer - Hue/Saturation. This will load your selection directly into the Hue/Saturation layer so that you can adjust the hue sliders and change only the colors you want to change!

Refining Layer Masks

If you have small unwanted parts in a selection, you can always paint over it with a brush tool on the layer mask.

Tip: If you hold alt/opt and click on a layer mask, it will appear as black and white. This can be very helpful for seeing tiny stray colors in your selections. 

Retouch with the Healing Brush tool
The Healing Brush tool lets you correct imperfections, causing them to disappear into the surrounding image. The Healing Brush tool matches the texture, lighting, transparency, and shading of the sampled pixels to the pixels being healed. As a result, the repaired pixels blend seamlessly into the rest of the image.

Select the Healing Brush tool . Click the brush sample in the options bar and set brush options in the pop‑up panel: Note: If you’re using a pressure-sensitive digitizing tablet, choose an option from the Size menu to vary the size of the healing brush over the course of a stroke. Choose Pen Pressure to base the variation on the pen pressure. Choose Stylus Wheel to base the variation on the position of the pen thumbwheel. Choose Off if you don’t want to vary the size.

Mode
Specifies the blending mode. Choose Replace to preserve noise, film grain, and texture at the edges of the brush stroke when using a soft‑edge brush.

Source
Specifies the source to use for repairing pixels. Sampled to use pixels from the current image, or Pattern to use pixels from a pattern. If you chose Pattern, select a pattern from the Pattern pop‑up panel.

Aligned
Samples pixels continuously, without losing the current sampling point, even if you release the mouse button. Deselect Aligned to continue to use the sampled pixels from the initial sampling point each time you stop and resume painting.

Sample
Samples data from the layers you specify. To sample from the active layer and visible layers below it, choose Current And Below. To sample only from the active layer, choose Current Layer. To sample from all visible layers, choose All Layers. To sample from all visible layers except adjustment layers, choose All Layers and click the Ignore Adjustment Layers icon to the right of the Sample pop‑up menu.

Diffusion
Controls how quickly the pasted region adapts to the surrounding image. Select a lower value for images with grain or fine details, or a higher value for smooth images.
Set the sampling point by positioning the pointer over an area of the image and Alt-clicking (Windows) or Option-clicking (Mac OS). Note: If you are sampling from one image and applying to another, both images must be in the same color mode unless one of the images is in Grayscale mode.
(Optional) In the Clone Source panel, click a clone source button  and set an additional sampling point. You can set up to five different sampling sources. The Clone Source panel remembers the sampled sources until you close the document you’re editing. (Optional) In the Clone Source panel, click a clone source button to select the sampled source you want. (Optional) Do any of the following in the Clone Source panel: To scale or rotate the source that you’re cloning, enter a value for W (width), H (height), or the rotation in degrees . To show an overlay of the source that you’re cloning, select Show Overlay and specify the overlay options. Drag in the image. The sampled pixels are melded with the existing pixels each time you release the mouse button. If there is a strong contrast at the edges of the area you want to heal, make a selection before you use the Healing Brush tool. The selection should be bigger than the area you want to heal and precisely follow the boundary of contrasting pixels. When you paint with the Healing Brush tool, the selection prevents colors from bleeding in from the outside.