Captain America Egg
Tape off the top half of the egg and paint it blue. Let it dry, and then remove the tape.
Tape off vertical stripes around the bottom half of the egg. Paint the stripes red, and remove the tape once dry.
Paint a large white star inside the top blue half of the egg.
Iron Man Egg
Paint the entire egg red, and allow it to dry.
Paint a yellow diamond in the center of the egg. Then paint two rectangles at the top of the diamond.
Fill in the diamond and rectangles with paint. Then paint a rectangle at the bottom of the diamond.
Paint lines from the bottom points of the rectangle up to each side of the diamond and fill in with paint. You may need several coats of yellow paint to cover up the red paint underneath.
Paint two white semi-circles for the eyes, and outline them in black. For the mouth, paint one straight black line and then a diagonal downturned line on each side.
The Hulk Egg
Paint the entire egg green.
Paint a zigzag hair line around the top of the egg.
Paint a white oval with a black gridline for the teeth in the center of the egg.
Black Widow Egg
Paint the entire egg black.
In the center of the egg, paint two red triangles, one right side up and one upside down, to create the black widow symbol.