Teardrops n Tiny Travel Trailers

I just cooked Chicken and rice in a Lodge DO. Something puzzles me. I've seen this before. When the meal sits in the closed pot after cooking, it has a tendency to turn dark grey. This is a definite color change. When the meal was done and I removed the coals, the color was normal. However, since I was taking this to a group gathering I left it in the closed pot to stay warm for about 45 minutes. When uncovered, Everything, particularly on the top had turned dark grey. Any ideas what's going on?

Was it lined with aluminum foil?

no

Was there any acid in the recipe, tomato, wine, vinegar, citrus? Acid can react with the CI and turn things gray.