Gently place eggs in single layer in large saucepan. Add enough cold water to cover eggs by 1 inch. Cover. Bring just to boil on high heat. Remove from heat. Let stand 12 minutes. (Adjust time up or down by 3 minutes for each size larger or smaller)
Pour off hot water and rapidly cool eggs by running them under cold water (or place in ice water) until completely cooled.
Mix 1/2 cup boiling water, 1 teaspoon vinegar and 10 to 20 drops food color in a shallow bowl to achieve desired colors. (Use shallow bowls so that the depth of the dye only reaches halfway on the egg.) Repeat for each color. Holding egg lengthwise, dip the egg into the dye for 5 minutes. You need to hold the egg up so that only the bottom half remains in the dye. Remove egg from dye and dry on paper towels. Dip undyed half of egg in second color, repeating the process so that only the undyed half is in the dye. As a variation, you can also leave a band of undyed white around the middle of the egg.