If you feed guppies goldfish flakes do they turn grey?

Feeding guppies with goldfish flakes will not cause them to turn grey.

Goldfish flakes may not provide guppies with the proper nutrition they need for optimal health and vibrant colors. Guppies are omnivorous fish and require a balanced diet that includes both plant and animal matter. A suitable diet for guppies should consist of live or frozen foods such as brine shrimp, daphnia, or bloodworms, along with high-quality commercial foods specifically formulated for guppies.