Hi @David_Ruder, thanks for reaching out!
The best way to set colors on Timeline is to create custom fields and set colors for each field. Then, when you set a custom field value on tasks, that color can be viewed on your Timeline.
You can choose “Asana Default”, which pulls from other colors you have set in Asana, or you can set your color logic based on custom fields. Once you’ve chosen which custom field you’d like to use, you can save that view for everyone, so your entire team will see the same color logic when they view the project in Timeline.
To set colors on your Timeline, click on the Timeline menu icon in the top right corner of your Timeline, then click on the “color” drop down to choose your color preferences.
I also suggest you to check this tip:
I hope this helps!