I believe the birds prefer red grit, and I trust their instincts more than mine. But either one is a good grit. so if that's all they have, it's no problem.
do they have oyster shell? If so, I would mix gray grit with 25% oyster shell for extra calcium, especially for the hens.
Thankyou! I didn’t know the difference was added iron so I appreciate the info!The red has added iron. I use the gray. I switched to the gray about 20 years ago.