The original sources had been lost, but some experienced gambler adviced us once: Bet 1 on Red and Bet 2 on Black.
This was meant to be better than just betting 1 on Black. The reasoning was not clear to us but here we go:
Betting 1 on Red and 2 on Black, means losing all 3 when Zero hits. This actually is worse than betting only 1 on Black.
Betting 1 on Red and 2 on Black, means winning 1, but losing 2 when Red hits, so effectively losing 1 when Red hits. This actually
is the same as betting only 1 on Black.
Betting 1 on Red and 2 on Black, means winning 2, but losing 1 when Black hits, so effectively winning 1 when Black. This actually
is the same as betting only 1 on Black.
So in summary, this strategy actually looks very similar as just doing a plain bet on Black, only it performs less
when Zero hits !.
The graph below shows the chance to come out winning with this strategy for 1 - 10 roulette spins.
Clearly the chance to win decreases the longer you play. The win% after 9 roulette spins with this strategy is 42%.
While with the strategy of betting 1 on Black (and nothing on Red) the win% after 9 spins is 47%.

So to conclude this stratey performs less than betting only 1 on Red/Black only.