This is a three unit cube inspired by David Mitchell and Francis Ow's 6 piece twisted cube which can be found here:
http://www.origamiheaven.com/new.htm
Around the middle of the page.
To make the unit:
Colour side down fold in half diagonally.
Fold two opposing points into the centre.
Fold the points back on themselves.
Turn the unit over and fold the edges into the centre.
Fold the unit in half colour side out.
Fold the ends into the middle.
Make sure that you fold this last step firmly.
Construction part one:
Lay the three units out and on the tip of the first panel draw a small a. Draw another A on the bottom half of the second panel. Arrange as shown and hide the A's.
Construction part two:
Tuck the end of the blue unit into the third panel of the purple unit. Tuck the green unit into the blue unit and finish with tucking the purple unit into the green unit.
Happy folding, Grace.