How do I plot all the decreasing parts of my time series and put them on my original time series data? I would like the

[answerhappygod]

How do I plot all the decreasing parts of my time series and putthem on my original time series data?
I would like the increasing slopes to be blue, decreasing slopesto be red, and the zero slopes to be 0.
My function has two vectors
1. t for time
2. Lx for Length in x-direction
Both vectors have components 1000000x1.