The ability that defines Renata's power works in all zones, not just the battlefield.

Mana symbols in the text boxes of permanents you control don't count toward your devotion to any color.

If a creature you control would normally enter the battlefield with no +1/+1 counters on it, Renata's second ability causes it to enter the battlefield with a +1/+1 counter on it.

If an activated ability or triggered ability has an effect that depends on your devotion to a color, you count the number of mana symbols of that color among the mana costs of permanents you control as the ability resolves. The permanent with that ability will be counted if it's still on the battlefield at that time.

If you put an Aura on an opponent's permanent, you still control the Aura, and mana symbols in its mana cost count towards your devotion.

A creature entering the battlefield at the same time as Renata won't get an additional +1/+1 counter.

Hybrid mana symbols, monocolored hybrid mana symbols, and Phyrexian mana symbols do count toward your devotion to their color(s).

Colorless and generic mana symbols (, , , , , and so on) in mana costs of permanents you control don't count toward your devotion to any color.