Practice the techniques used to produce mandala sand paintings. Place a liberal amount of sand in a plastic or glass container. Mix in dry tempura dye until you've achieved the vibrancy you seek.
Repeat the first step for each color you want in your mandala.
Use your drafting compass and pencil to draw a circle on the top of your table to form the outside frame of your sand painting.
Sketch with pencil your mandala, as intricately as you'd like, using the compass again to make as many internal circles as you'd like, and even small concentric circles around one internal loop.
Choose which colors you'll place in which areas of your sand painting. Various techniques are possible here, from using one color to fill one complete area of the mandala, or stripes of colors can be layered into an area to form waves of color. If you have a sand funnel, use this for the most even application; if not, use a spoon carefully to layer on the different colors of sand.
Study the work of known masters of Tibetan sand paintings to hone your technique.