Can't (easily) see additions on certain terminal themes

[thislooksfun]

Not sure if this is really a bug or if I'm missing some setting, but none of them seemed to apply to my situation.

I'm using the default macOS Terminal application with the Homebrew profile, which is green text on a black background for the retro terminal look, however it just does not play nice with difftastic:

/// file1.ts:
function helloWorld() {
  console.log('Hello World');
}

/// file2.ts:
function helloWorld(name: string) {
  if (name) {
    console.log(`Hello ${name}`);
  } else {
    console.log('Hello World');
  }
}

It would be nice if there was some way to override the default (unchanged) text color to be something other than the terminal default text color so I can actually see where the additions are.

Alternate solution: dim the non-relevant (non-addition/deletion) text to provide more of a visual distinction. Being able to change the base color is preferable, but this would still be an improvement.