it bleaches them lightening the wood / hydrogen peroxide is a bleaching agent. also ruins the sealer/finish if it is spilled on finished wood
It will bubble and ruin the existing finish. It is a bleach agent, and will lighten the area.
At 3% over-the-counter solution, it probably won’t bleach them as much as it will cause water damage.
What are you trying to achieve?
Regular peroxide bought at the store probably won't do much, but it is best not to add it to wood.