My site is in red although I have no open actions and very few points in red, why is this?

There are symbols showing the status at each level which actually roll up from the lower levels. Thus, if there is an alarm at a measurement point (the lowest point of your entire hierarchy), this will roll up through the hierarchy to the organisation level.

In the example above, the alarm on the Glacier filter measurement points rolls right up to the AVT Sales Demonstration organisation level.