The look and feel of a gauge can be formatted using the Display Options Icon 
A pop-up window appears and the Gauge can be formatted and configured using the Gauge - Display options Screen.
A Gauge can only show a single measure value and this field and value is shown here along with the expression used to calculate the gauge value.
Note: Changes made to the Gauge can be previewed using the 'Apply' button. Pressing 'OK' will save the changes.
The Display Options screen is divided into numerous sections
1 Gauge Settings
2 Colour Range
3 Dimension
1. Gauge Settings
1.1 Gauge Type - The style of Gauge can be selected using the Gauge Type dropdown:
1.2 Scale - The scale (start point and end point) of the Gauge can be fixed here i.e. 2,000,000 to 5,000,000. 
2. Colour Range
2.1 Show Traffic Light (Tickbox) - Show the traffic light colour on the Gauge (Orange Circle in above Gauge)
2.2 Colour Range - You can specify multiple range values (Min/Max) here plus the associated colour to be shown on the Gauge for values falling in these ranges.
Colour ranges specified can be edited by pressing the 
edit Icon or deleted using the 
delete Icon:
3. Dimension - Here, you can specify the dimension of the component in pixels.