Set default color mode extra parameters

[lavigne958]

What you expected to happen?

I expected to be able to set a color for my Stat or TimeSeries panel. Specificaly the fieldConfig.defaults.color.fixedColor option.

What happened?

I can only change the entry that sets the mode for the color but not the color value for that mode.

How to reproduce it?

Create a new Dashboard, add a new panel of type Stat, set the option colorMode, it takes a string as argument but it should take a dict object where we can set the mode to values offered by grafana (like: fixed, threshold, etc) and set the value field that actually change name depending on the mode value, in case of fixed color value the key will be fixedColor and the value is a string that contains the RGB values like in CSS rgb(0,128, 64)