I Spy with My Little Eye... Oops!

So, you know how kids love playing I Spy? Well, my two munchkins are obsessed. It's like a never-ending game of 'find the random object' that could be anywhere in our house or on our trips. One day, we were at the grocery store and I told them to use their eagle eyes to spot something blue. My eldest finds an item and excitedly says it's her favorite purple crayon but insists she was right because magenta is basically red and red can turn blue somehow (you try explaining color theory to a five-year-old). Meanwhile, my youngest just grabs anything he thinks fits the description without asking questions. Last week at the beach, I called out 'I spy something shiny.' They both scrambled around like puppies on a hunt until little Max snatched a pebble and shouted triumphantly it was a diamond! The look on his face made me laugh so hard, but then my wife gave us one of those 'what have we created' looks. Am I the only parent who uses this game as an excuse to buy candy or find random items? Is there anything more fun than seeing how high their eyebrows will go when they think they've won with a bottle cap from the recycling bin? Any tips for getting them back into reality without crushing their enthusiasm? Or am I just supposed to enjoy these moments?