Property values mode
This video bar will show the object's property values - how and when the varying properties change throughout the sequence.
Open it by clicking on the dropdown and select Property values.
The property bar shows the name of the property, the value and when the value has been changed.
Each change/ edit to a property value receives a new color. The colors are NOT assigned to a specific value. So a value changed from A->B will not share the same color as B->A. The color only indicate that there has been a change in value not what that value is.
If there's a object property error (e.g. the property has no value) it will be indicated by the color red along the timeline.
If the bar is grey it means the object is not visible in that or those frames.