Look at other discretization schemes (or at least disable feature for non-tpfa, non-box)
Add guards in case TBB is not available.
Guard for gridviews which are not thread-safe.
Check caching (due to coloring this should also work with caching)
Option to set number of available threads at runtime
Check efficiency of coloring scheme (efficiency doesn't matter much for instationary simulations).
The constraint behind the coloring should be: Two elements that modify the same entries of the matrix or the cache or any other global object shouldn't have the same color. In the graph coloring sense: Two elements (two nodes) that do modify the same entries are connected by an edge.
