Thanks @jhackney1972 for helping me getting the dimension color changed, here I will provide a summary. Note this is not a feature in the UI, it would involves editing one of the Fusion 360 application supporting files. Windows only
Step 1: Make sure fusion 360 is closed, you wont see the change until you restart Fusion 360.
Step 2: Go to path:
C:\Users\{1}\AppData\Local\Autodesk\webdeploy\production\{2}\Neutron\Server\Scene\Resources\Environments\{3}
1: Your computer username
2: It will look like random sequence of letters and number, find the latest folder (eg ad7294217f9be3f5795b94fde199c32032296a4e)
3. The environment you want to change (eg PhotoBooth)
This method will apply the color change to the environment you selected.
Step 3: Edit the {environment}.xml file (eg PhotoBooth.xml)
If you would like, create a copy of this file before editing for backup.
You will need to use a text editor for coding such as Notepad++, Sublime Text, or VS Code.
Locate the line that contains SketchDimensionColor:
<SketchDimensionColor ARGB="1 0 0 0" />
Here the 4 numbers after ARGB here correspond to the color value, the first color is opacity the other three is the RGB setting from 0-1. Usually you want the opacity to be 1 to keep things visible, so just change the other three numbers. This is what it looks like changing the color:
<SketchDimensionColor ARGB="1 0.52 0.87 0.35" />
If you don't know how to edit the value or what it will look like, the same file {environment}.xml also contains sample color values at the bottom if you search for "ColorCycle", for example:
<ColorCycle name="Dark Green" RGB="0.52 0.87 0.35" />
Step 4: start Fusion 360 and see if the changes are there.