The colors weren't as vibrant as what I had seen on Pinterest, but it was a nice color combination, just the same. The kids all took turns squeezing the vinegar out of the dropper and onto the baking soda, which was a nice little bonus for the two younger ones as it helped work on their fine motor skills too! The two older kids enjoyed mixing the colors later to get different color combinations. It took quite a while for the fizziness and the excitement to go away, but here's what it looked like as the liquid was just starting to dominate the baking soda.
And just so we don't end on the ugliness that is the "science experiment" picture, here is a picture of what my nephew and my son (the half naked one) did after they finished with the experiment. You'll never hear me say toddlers are too young to do the dishes... :)