I have boy/girl twins that share and room and started by going with a sage green wall color with a plan to create custom headboards (an easy diy) to personalize each sides of their space. Pulling in some pinks and blues on the girl side of the room and other greens and blues for the boy side of the room. To keep the cohesiveness of the space I stuck with solid light blue comforters. That balanced out the fact that my daughter had floral headboard and my son had striped headboard. To keep it simple start with an over all neutral wall color an add some individual personality with a custom headboard that pulls in coordinating colors or with fun throw pillows and lamps.