I found myself not so clear in the original post that
I forgot to mention the shape of one label might change but the ID remains the same before disappearing.
So I don't want the colour for same labels change and I want different IDs with different colours in a short time period.
e.g: the orange, red and purple labels exist around t18 -> t19 -> tn
The biggest problem is the ID easily exceed the limit of colours for labelvolshow (recently I found it is 128) after t30.
All the labels become same colour.
I guess reusing colours is ok as long as these different labels can be distinguished by time
But I'm not sure how to do it.
Thanks