When picking a shade of blonde, consider one that's of an opposite tone to the one of your skin. If you have a warm skin tone, go with a cool tone, and if you have a cool skin tone, go with a warm tone for your hair. A good rule of thumb is to not go more than two shades above or bellow the natural shade of your hair.
If your skin has pink undertones, dying your hair a warm shade of blonde can result in your skin looking flushed. If your skin is olive-toned, a golden shade may work best. For example, you can try strawberry, buttery or honey shades of blonde. If you have a neutral skin tone, both cool and warm undertones work well for you.
If you don't know how to figure out the tone of your skin, try looking at the veins on your wrists. If they look blue, then your skin is cool-toned. If they look green, your skin is warm-toned. If this method doesn't work, you can also try putting a white t-shirt next to your face. If you appear blue, then your skin is cool. If you appear yellow, then your skin is warm.