The Tortoise is a symbol of water and longevity. It is believed to have assisted good and evil forces, in the churning of the ocean that provided the nectar of immortality.
The yellow used in the illustration symbolises the colour of the Sun - the source of life - and is associated with virility. The concentric, radial patterning, similar to ripples in water, at the four corners of the illustration give the illusion of continuity and harmony.
P.S. Anything names after the tortoise should be taken slow. It’s only right, And why would you want to hurry something like this, eh?