Avoid the E. A. Wallis Budge books if you go for something of textbook quality.
Big things in Egyptian Mythology: Duality (Light versus Darkness, Order Versus Chaos, Interconnectedness of the living and the dead). Honestly, Transform (Day and Night sides) would be a GREAT mechanic to convey how Egypt would look at the universe. We'd probably also want to play with the graveyard somehow as in Egyptian thinking the world of the living and the world of the dead can affect one another -- your existence in the underworld persists as long as any part of your self persists in the known unierse.
There are up to seven parts of the 'soul' depending on how you look at it. To use wikipedia's english terms the five big ones would be your Heart (emotion/will), Shadow, Name, Personality, and Vital Spark. The body and a complicated immortal essence referred to as the Akh in some texts are 6 and 7.
It would be easy enough to map the five main parts of the soul to the five colors. The Heart, as emotion and willpower without identity is very much
. The personality -- your intellectual identity -- on the other hand maps to
. The vital spark, the losing of which is the difference between alive and not alive? That's
. Name, as an idea of solidity and categorization fits nicely into
, and the shadow is pretty naturally