To be able to change the colour of text in widgets would you just use different widgets and use programming to display or hide the appropriate ones?

You cannot dynamically change the color of text unfortunately. To do what you’re saying though, I would just use a lamp gauge with the same text as different lamp gauge elements but each element would use a different color. Then by simply changing a value in the database variable to which you've attached the lamp gauge, you can change the color of the text.