It is better UI/UX practice to mark FAILED positionals differently, not successful positionals. If you mark successful positionals, there is still no way to tell just by looking at the numbers if a normal colored attack is a missed positional or a non positional. If you mark failed positionals instead, then it's really easy to see which attacks are failed positionals.
Take a look at these two schemes:
Marking successful positionals:
Twin Snakes 429
Demolish 421(+)
Bootshine 660
True Strike 499
Snap Punch 439
Dragon Kick 309
Twin Snakes 418
Snap Punch 459(+)
Bootshine 628
True Strike 503
Demolish 435(+)
Dragon Kick 318
Twin Snakes 400
Snap Punch 420
Bootshine 655
True Strike 518
Snap Punch 504(+)
Marking failed positionals:
Dragon Kick 325
Twin Snakes 429
Demolish 421
Bootshine 660
True Strike 499
Snap Punch 439(-)
Dragon Kick 309
Twin Snakes 418
Snap Punch 459
Bootshine 628
True Strike 503
Demolish 435
Dragon Kick 318
Twin Snakes 400
Snap Punch 420(-)
Bootshine 655
True Strike 518
Snap Punch 504
How many failed positionals were there? Without knowing the attack names or monk rotation, would you be able to tell which actions were failed positionals? The second example, with the failed positionals marked, is clearly much easier to interpret.
It is also bad UI/UX to indicate things only by a change in color. There needs to be something different about the text. For example, add (-) to the end of a failed positional.