I can't change font color in wiki on github.
<div style="color: red">test</div>
<font color="red">test</font>
Unfortunetly, You cannot include style directives in GFM.
Here is the most complete "Markdown Cheatsheet", and it shows that this element <style>
is missing.
That being said, you can use diff code style highlighting for red and green:
```diff
+ this will be highlighted in green
- this will be highlighted in red
```