This brings up a display similar to the one below. This view represents relative lifetimes of the threads, represented by the length of the horizontal bar. The position of the horizontal bar represents when in the lifetime of the program these threads existed. The bars are also color coded to indicate how much of the thread's lifetime was spent in each of the possible states. The colored bars can be very useful to help determine which threads to consider when trying to optimize applications.
Cool colors imply some sort of idle state.
You should investigate these threads to see if this is absolutely necessary, or if there is a way to reduce their CPU utilization. A pie chart of the percentage of time spent in each state is available for individual threads by double clicking the thread. This is a useful way to determine how a thread is dividing its time. Another technique is to mentally draw a vertical line down the thread histogram to see which threads and how many of them existed at a certain period. You do this by noting for which threads the vertical line intersects a horizontal bar.