Wrote this based off a post my friend made on Tumblr. Enjoy!
"Molly, it's not working!"
Sherlock was bent over the sink in Molly's tiny apartment bathroom, his fingers gripping the edge of the gray ceramic bowl so hard his knuckles were turning white. It was three days after Sherlock went over the edge of St. Bart's, the scrape on his cheek was healing, and the swelling on his turned ankle was going down. He was getting ready to head out of London and down towards Minsk. The first stop on his mission to eliminate Moriarty's remaining web.
Sherlock was dying his hair. Molly had suggested ginger, as it would be a drastic difference to his dark curls. The problem, however, was that one box of dye wasn't enough. The detective spent forty five minutes with a scowl on his face and red-purple paste in his hair, only to find, after he washed it out, that only his roots had any noticeable ginger colour to them.
"Well, that's why we bought three boxes. You can't expect hair as dark as yours to change instantly Sherlock." Molly was trying to hold back a giggle at the sight of Sherlock's hair, and was a little sad no one else was around to witness it.
Sherlock sniffed, his face wrinkling just enough to show his level of annoyance with this process, and then grabbed the second bottle of hair dye off the sink counter. He emptied a sizeable portion directly into his hands before running them through his still damp curls. He heard Molly muttering something about using gloves but he just ignored her, applying more dye to his hair in a vigorous manner that was sure to take out a few hairs.
"This had better work." He grumbled, staring at himself in the mirror. A drip of the red-purple paste ran past his left eye and down his cheek, making it look as if blood was on his face. He looked very similar to just as he did after he fell. It wasn't his blood then, either. The thought only caused him scowl deeper.
Forty-five minutes of waiting, and Sherlock decided he needed to wait another twenty minutes. He didn't want to have to repeat this process one more time.
Twenty more minutes of waiting, and he wins the argument against Molly to wait fifteen more minutes. His hair falling out would look better than half-ginger hair.
After fifteen minutes, Molly shows superhuman strength and manages to get Sherlock's hair underneath the showerhead long enough to get most of the dye out before he shoved her out of the bathroom to finish it himself.
Sherlock ran a towel over his head when he was sure all the dye was out, then faced himself in the mirror. When he pulled the towel off, his scowl deepened even more. The roots of his hair hadn't changed any colour, his tips were a soft orange colour, and everything between was a mash up of ginger and light brown. He gripped the edge of the sink again and squinted his eyes closed as Molly opened the door.
"This was a terrible idea, John!"
Sherlock stiffened. Molly stiffened. Sherlock's eyes shot open wide and he stared at the patchwork colour of his hair. Molly stared at Sherlock, her fingers gripping the mug of tea in her hand like her life depended on it.
That's right, thought Sherlock, John isn't here. He won't be here, not for a while. Sherlock knew he wouldn't be around John, knew that wasn't possible. But this was the first time he'd said John's name since he said goodbye, and the first time he realized John wouldn't answer him. Not for a long time. He didn't know how long. John…
"Sherlock?" At the sound of Molly whispering his name, Sherlock ran a red stained hand over his face before picking up the third bottle of dye and emptying it onto his head. He sat on the edge of the tub and let Molly help work the paste into his curls as he just sat in silence.
"Third time's the charm, right Molly?"