It is one of the many life lessons you learn in the casino. Gambling, like life, is loaded with streaks. Many gamblers bet streaks so they won't get emotionally involved in bucking a trend. But along with the above advice comes this caveat. For a gambling analogy, note the agate type at the bottom of a mutual-fund advertisement.
Past performance is no guarantee of future results.
In other words, just because red appeared five times in a row, that does not mean it will happen again. Assuming you are playing on an unbiased wheel, the ball has no memory, and red can appear again or not for the next 20 spins. Also available are quinellas, exactas and even some prop bets. My personal favorite is betting individual drivers against each other. An example of this would be Geoff Bodine in the QVC Ford finishing higher in the race standings than Ward Burton's MBNA Pontiac.