This is an activity I do with my kindergarteners. They have to color in the vowel (on the front side) according to a color I decide. In this activity, they are synthesizing vocabulary and language they hear to perform the task of coloring the page.
On the 2nd side, I have the students point to the letter I say in Spanish. Though, you can have them color lightly over each letter or do something else with them. Change it up to meet your students' needs!