Owing to a strange confluence of tiebreaker scenarios, the Colts' game today against the Dolphins has virtually no impact on its playoff chances. According to my simulations, the Colts make the playoffs in 6.7% of the simulations in which they win, and in 6.1% of the simulations in which they lose., a swing of just 0.6%.
Contrast that to the impact the Texans-Titans game has on the Colts' playoff odds: The Colts make the playoffs in 18.7% of the simulations in which the Texans lose, and just 0.2% of the simulations in which the Texans win.
In a nutshell, the Colts need the Texans to lose out. If that happens and the Colts lose today, but win next week, they tie the Texans, but would win the tiebreaker on divisional record. If the Colts win today and win next week, they win the division outright, no tiebreakers necessary.
But if the Texans go 1-1 in their final two divisional games, the Colts need to win their last two games just to tie the Texans. In that scenario, the two teams would tie on divisional record, record against common opponents, and conference record. After that, you're on to strength of victory (combined win percentage of teams you beat). And it turns out that the Texans generally hold an advantage on that tiebreaker over the Colts, although the last two weeks could still swing that outcome (but it gets complicated).
If you're looking for independent verification of this, you can check the Upshot's fantastic playoff simulator, which similarly shows that the Colts' playoff chances hardly move at all in response to the Colts-Dolphins outcome.