Hindu Prana Yantra
Yantra are graphic mechanisms for triggering access to various goals of meditation. Mastery of Focused Awarenes and Absorption in the Yantra increases the strength of the Prana Force permeating the physical body. The Yellow Color Energizes and also increases the Power of Ones Faith, which is in part, Synonimous with Focused Concentration (Samadhi).
Image Source;
http://www.shantivan.org/