TatukGIS by default does not store colors, etc. with the shape geometry. Instead, we prefer an object model in which important information about objects is stored as attributes and the program renders colors based on attribute values. Therefore, the best way to store object color is create a special attribute field to store some shape designator like an object category and render based on this.
It is also possible to store the numeric value (RGB) of the color in an attribute field and just select the Color (in the visual layer properties control) to be rendered from the attribute field.