abstract:In poker, pot odds are the ratio of the current size of the pot to the cost of a contemplated call.Sklansky, 1987, Glossary Pot odds are often compared to the probability of winning a hand with a future card in order to estimate the call's expected value.
That explains the significance of the red ball: it makes the odds of winning the pot less likely since you have to match all of the white balls (generally from 1 to 50) plus choose the correct red ball (out of a different set of balls, generally 1 to 35).