Paint the first layer on the pastel sheet or canvas board using the blue pastel. Since turquoise is predominantly blue, start with this color as the first layer and slowly incorporate additional colors until you reach the perfect shade of turquoise.
Apply a soft layer of green pastel to the first layer. Depending on the shade of turquoise you desire, you can work with a lime green or a darker forest green.
Blend the two colors together using either your fingers or a styrofoam pellet. If you feel that you've added too much green, go back and add a touch more blue to balance the two colors.
Continue steps 1, 2 and 3 until you reach the ideal shade of turquoise. Depending on the desired texture of your art piece, avoid over-blending the blue and the green. The more you blend, the smoother the texture.