Determine your skin tone first in order to determine the best shade of blonde that will complement that tone. Typically, cooler skin tones match best with cooler blonde shades, whereas warmer skin tones work best with warmer blonde shades.
In order to determine your skin tone, stand in front of a mirror under natural light. Make sure your face is makeup-free and you are wearing light-colored or white clothing. Observe the overall undertones of your skin rather than the small variations. If your overall skin tone is neutral to pink, you are a cool tone. If your overall skin tone is yellow to reddish, you are a warm tone.
Keep in mind that eye color and makeup choices also play a factor in your overall look. The hair color you choose should complement the tonality of your eye color. If you are making a subtle change in hair color, you only need to make minor adjustments to your makeup; however, more drastic hair color changes require major adjustments in makeup color.
If you are looking for a contrasting look, choose a cooler shade of blonde if you have a warmer skin tone and a warmer shade of blonde for a cooler skin tone. You can also create contrast through eye makeup and blush color.