What does Vivaan mean?
Commonly glossed as 'the first rays of the morning sun' and associated with Surya (the sun). It is a modern Sanskrit-derived name; the popular claim that it is an epithet of Krishna rests on weak sources, so treat that association cautiously.
What does Aarush mean?
From Sanskrit arusha (आरुष), 'reddish, red of dawn', commonly glossed as 'the first ray of the sun'. The 'red/dawn' sense is the attested one; 'first ray of sun' is the popular reading.