There are four key points to think about when designing a dashboard: Colour, Consistency, whitespace and communication
Colour
The most important thing we need to think about is using colours that are visable. This means that the colours aren't too close together meaning that writing or details are not visable.
We also need to be aware of people that are colourblind - the most obvious combination of colours not to use is red and green. The best way to check if the most common colourblindnesses are being accounted for is to use online softwares such as colblis
Use colours sparingly, personally I would only use colours that are not on the white or black scale for highlighting the most important details
Consistency
Use the same alignment of text, charts, headers etc. etc.
Having equally spaced bars in a bar chart
Using the same colours to highlight the same things
Equal padding on charts
Whitespace
Use padding!! Use uniform padding and use it to make sure that the dashboard isn't overwhelming to a viewer
Using dividers (blanks with colour and lots of padding) to break up bits of a dashboard. Maybe this can help to break up the narrative or just improve the flow or logic of a dashboard.
Communication
Let users know about any interactivity
Let users know what the dashboard is about - using titles and headings for graphs is the best way to do
Let a user know what they are seeing - again achieved by titles and headings
However... I am sure by the time I get out to a client half of these ideas will go out of the window due to factors including businesses colours and what a client wants.