They were also able to answer the question, "Why don’t the colors mix right away?" While digging around for information, they learned about a term called stratification. The immediate definition of stratification is the arrangement of something into different groups, Water stratification is all about how water has different masses with different properties and this may create the barriers that you see among the colors of the candies.
Still other sources talk about how each skittle has the same amount of food coloring being dissolved and as they concentration of this color spreads out similarly they don’t mix when they meet up with each other.
What do you think?