Steps to reproduce:

1. Create a new graph widget on a dashboard
2. Set up an item to graph using a red colour
3. Set up problems for the host to be displayed on the graph

Result:

Since problems are overlayed on the graph in red with no option to choose another colour, it can be very hard to see red-coloured graph items as the reds all merge together visually. It becomes increasingly difficult to see these items as more problems get overlayed at the same time.

Expected:
Facility to adjust the colour and transparency settings of the problem overlay, just like we have for graph items. Ideally, this should allow continuing to show the problem bar underneath the graph's x-axis as now, but without any colouration being applied to the main graph body.