On that far off day the littlest angel was bored and lonely. She was too tiny to join the weavers that made the clouds and she couldn't speak well enough to sing in the Heavenly choir. She missed her mommy and daddy, who weren't angels yet. She spent a lot of her time just watching down where they lived from an out of the way corner of Heaven, crying down little angel tears on them. After she ate her grilled cheese sandwich and soup for lunch that day she went to the place where she knew God would be having his afternoon coffee with the prophets. She tugged on his robe gently to get his attention.
When the Holy one saw who was trying to talk to him he gave the command for everybody else around the table to be quiet, for he knew that she couldn't see or hear very well, and that she had trouble talking. He loved her all the more for it.
"Yes my little one, what is it?" He asked her.
"Please God, " she asked him, tears of loneliness streaming down her face "I have been looking down at where my mommy and daddy still live, looking at the beautiful flowers there in their garden, and I'd like to go down for a closer look."
God knew that where her folks lived it was winter and there were no flowers there so he said, "There's no flowers."
She, with her bad hearing thought he said, "They're snow flowers." because she knew it was winter too. She said, "Oh look. They're beautiful."
When the Lord followed her gaze to where she was pointing he realised that what looked to her like flowers in the snow was actually the light streaming through the stained glass window of the church next door to her parents' house, and that it was indeed beautiful. He told her she could go look if she wanted, but to go no farther than the tops of the trees. Then, he put it in the minds of all of his followers that they would like to make coloured lights shine in the snow, just the way the lights of the church shone for the littlest angel on that day so long ago.
That's why we put up coloured lights now at Christmas, and why angels come to this day to the tops of the trees to look at them and be close to their families.