or pretty much anywhere else , the best colour for the background is white.
It is the colour schemes used for the charts , slicers and other individual elements which really differentiate between a great design and a bad design.
Having a wonderful background does nothing to what the dashboard is actually supposed to present viz. data and the implications of the data.
If you take a look at the following 2 dashboards , you will appreciate the work that has gone into creating them ; the selection of colours is good , but after going through the dashboards and using them , what will stay with you is the creativity and hard work that went into their development rather than their use of colours ; using good colours heightens the user impact , but the greatest impact is in the design of the dashboard itself. Bad colour selection can certainly impact the user , but the basic thing to remember is to avoid dark colours , and go in for the lighter shades.