I have four. THis is what we have done. Not saying this is for everyone.
My oldest at 14 wanted black, I nixed that one but said OK to the granite paint in grey. So the bottom was granite grey and the top a lighter grey with a wolf border and wolf curtains. North woods themed pictures and accessories. It was a nice room.
THE downfall--we had to sand all that granite paint off and paint it neutral to sell the house.
The girls, same house with the wolf room. I came up with this great idea of painting a mural on the whole room. So it was a meadow, with a house and barn and picket fence. We had a cow pasture, sheep, strawberries. A weeping willow and an apple tree, I hung apple ornaments from the tree and a hummingbird feeder from the willow. One of the walls it had more of a foresty feel, more trees. So we got dancing bear wallies.
THe baby, I painted the room white. The border was a chunky dumptruck/car/firetruck border. THat went into the middle. I painted the window ledge like a street, Behr actually has a color asphalt, it had a yellow line down the middle and a stop line. His matchbox cars could fit on it. Under the border I ran one of his trucks through the asphalt paint and on the wall.
We've mioved twice from that house.
2nd house we got to paint, the girls had each wall a different pastel color.
My baby, he was 5-9 had a tan wall with a fish border and I painted plaid stripes underneath.
My oldest moved out before we painted anything in his room.
One of the girls took it over and turned it purple.
THis house my 13 yo daughter painted hers kelly green with white trim. She has white foam daisies running along the top.
Her sister's is the same purple.
The baby is now 10 and we are doing a forest mural starting this week.
Tell the kids what you do not want--no black, no fuschia, kelly green is beautiful when I shut her door.
Take them to Lowe's and let them see all the colors.
Pick a few everyone likes and take it home.
Buy a few cans of samples, these are $3 ish from Lowe's.
Let each child have two walls.
Let each child have half a wall, oldest gets the top, younger the bottom
Let one child pick the room, the other the accent and run a line or pattern with the accent color.
Paint it neutral and let each have their own style of bedding.
Or go all out, it really is fun to see a room be transformed into a dream world for them. I find blank walls begging for embellishments.