it is absolutely okay to say "God bless you" to someone as a kind and well-meaning expression. People often use this phrase as a way to wish someone well or offer blessings in various situations.
When communicating with others, it's essential to be respectful of their beliefs and preferences. If you know that someone follows a different religion or doesn't believe in God, you can consider using a more neutral or secular expression like "Bless you" or "Take care" to convey your good intentions without assuming or imposing any specific religious belief.
Ultimately, kindness and good intentions in our interactions with others are what matter most, regardless of the specific words we use.