Your new Croton 'Tamara' is unlikely to become more variegated, but keeping it on a sunny windowsill will enhance that possibility. That is true for all Croton species. With hybrids such as 'Tamara,' there is a tendency for them to revert to the original species form and variegation as they age. Other than light, you have little control over the variegation. Enjoy what you have because it looks like a healthy plant.
