Are you teaching long and short vowels? Use this 5-page packet. It includes long and short vowels for a, e, i, o, and u.
Each page has 15 pictures of long and short vowels. The directions tell the students to color the long vowel pictures one color and the short vowel pictures a different color. Each direction is specifically given. For example, on the A worksheet, for long vowels, it says "-color these pictures red" and for the short vowels it says, "-color these pictures yellow."
I also have another packet that is exactly like this here