When you are trying to match a color in nature, decide if the color is warm or cool. When looking at the color of an object, decide if the color is more bluish or yellowish . All colors will be one or the other. Even grayed tones will have some bluish or yellowish tones. When in doubt about how yellow or blue it is use a grey color.
Colors have value .
This is the degree of light or dark. In general it is the amount of white or black mixed with the paint. Compare the color to others in the scene and decide if it is lighter or darker. The value of a color can be determined by imagining it in black and white. Colors that are different can have the same value.