This is the 5883rd most frequent Japanese word.
まぜる
"まぜる" means "to mix."
Here, 'まぜる' refers to the act of combining colors in describing a cause-effect relationship.
その色をまぜると紫になります。
If you mix those colors, you will get purple.
In this sentence, 'まぜる' is used to describe the action of stirring the coffee upon adding sugar.
私は砂糖を入れてコーヒーをまぜた。
I added sugar and mixed the coffee.
In this sentence, 'まぜる' is used in the imperative form to instruct someone to mix the eggs.