The Mark at 200 can be set using a reference line this can be static e.g. 200 or based on an expression.
It is not possible to do what you want with colours on this gauge. Achievement is marked on the gauge as another line like the reference.
The coloured segments are there to identify when your achievement is moving from one area to another these areas can be set statically or by expression.
Some things you can do with gauges in the example above I have a lot of gauges on the screen so some of the features of the gauge are missing e.g. Achievement Value which I included myself in the gauge sub header.
I set min and max size if the gauge based on the min/max requested value. Note check for extreme outliers if using this approach.
I used segments to define the target and used the footnote to display the value.
Hope this helps
Have you thought about implementing "Bullet Chart" for your analysis?
I saw one in Github, whihc was developed by "Seebach".
YOu should try addign this extension to your app. give it a try.