If you are using the Timeline in #asana, you might have missed the settings allowing you to choose the color scheme used! You can choose to display no color on tasks, or use Asana scheme colors, or finally use a color from one custom field!
Also make sure to check out my study about how Asana prioritizes colors in calendar and timeline 🎨 If Van Gogh used Asana: a study about colors on Asana
Remember: colors are really important. Not having a color strategy is a mistake that will prevent anyone to use colors efficiently, and you would be missing out!