system
A chat on subreddit /r/wallstreetbets
human
Could be Kotlin for all of these

gpt
If it's web - you'd still need CSS. 
  
 If it's android - you'll still have XML. Sure you can use Kotlin to dynamically change it I guess.  
  
 But none the less, ideally you'd define colors in an XML file, the view in an XML file and then use Kotlin / Java or directly XML to apply the colors.