This idea came to me while enjoying a Blueberry Ring Pop and someone pointing out that my tongue was blue. Thus was the birth of this lil beauty.

Amy had insisted that the Doctor take a break after their little adventure on the Orient Express. Rory was off in the library reading some sort of book about Romans, he'd been obsessed with them after he had been one. The Doctor was of course fiddling with something on the TARDIS Amy had walked to the kitchen to find a snack, and she found a Blue Ring Pop, she hadn't one of those in ages, so she took and walked to her and Rory's room to have some alone time. She continued to enjoy her little treat as she flipped through a magazine she found. When she finished she tossed the ring in the bin along with the wrapper, and walked out of her room to the Control Room to what the Doctor was up to.

"Rubbish" she heard the Doctor exclaimed to the air.

"Doctor" she said she walked down the stairs,

"The Hot Valve, why is it here? I mean what could we possibly use it for, its not like we'll need to flood the TARDIS with hot water." he said standing up, "Again" he amended

"You had to flood the TARDIS with hot water?" Amy asked giggling, he scratched his head and glanced at Amy and did a double take

"Bliminy Christmas" he said eyes growing wide and rushing up to Amy

"What?" she asked not understanding his sudden frantic state,

"Say Ahhhh" he said he said and she complied, "Your tongue is blue" he said,

"Oh this is not good..No it's worse its extremely VERY not good" he said ringing his hands,
"RORY!" he bellowed, then Amy heard a crash and sound of footsteps
"What's wrong?" he said running down the steps,

"Okay Amy keep your mouth shut and uh don't panic" he said wiggling his fingers and mumbling

"Why do-" Amy began and the Doctor shot his hand to her mouth, Amy rolled her eyes,

"Okay tell me EVERYTHING that you have been doing from the moment you woke up" he stated, Amy opened her mouth to do what he said then he's hand slammed back to her mouth
I told you to shut your mouth" he said

"Erm...I'm a little lost" Rory looked back and forth to the people in front of him.
Amy pointed to herself and made the number sign

"Okay Amy's tongue is blue which is Indigo which affects the mouth, resulting in a blue tongue as a warning symptoms, and you skin begins to turn blue" he said

"How do you get Indigo?" Rory asked scratching his head

"You consume a blue candied diamond ring" he said

Amy's eyes grew so wide the Doctor feared that they would pop out of skull he seen that once took ages to fined the other one.

"Why can't she talk?" Rory said
"Well once the the ingested ring dissolves into the blood stream it then becomes an airborne pathogen" he said

Amy then began to jump up and down

Getting the attention of the two men

She pried the Doctor's hand from her mouth and she began to mime, she pointed to her wedding ring
"Yes Amy it's a very lovely ring, Women and jewelery" he complained

Amy rolled her eyes and then grabbed the Doctor by the ear and led him to her room with Rory in tow.

She reached into her bin and pulled out the wrapper and plastic ring.

"Ah" he said realization hit him and after that hit him, Amy slapped him on the forehead

"Oi I'm the only allowed to that" he said as he straightened his tie.

"Okay then to the TARDIS sick bay" he through out his hand in a charge motion.

Once they arrived in the sick bay the Doctor rummaged through the shelves and pulled out a syringe with multi colored liquids swirling about, and walked over to Amy and injected her without and she winced only for a moment then the pain went away

"Ahhh" he said opening his mouth wide and she opened her mouth

"There good as new" he said as he popped a sweet into her mouth and patted her on the head.

"Now what have we learned?" he asked sounding as if he were talking to reprimanded child

"Never eat Blue Diamond Rings" Amy whined

"Yes though, I don't know why I stopped it, a blue ginger" he joked and started laughing

Amy narrowed her eyes at him, his laughter stopped

"Oops" he said and started running with Amy chasing after him.