Playing Uno this weekend, one of the players played a Wild+4 but chose the same color that was in play (this led to a successful challenge). I had thought that, regardless of what's in the player's hand, the player could not choose the same color after playing a Wild+4 - it had to change to one of the other 3 colors. A player could choose the same color after playing a regular Wild, though.
Looking at the rules, though, I did not see this restriction; only that the player playing the Wild+4 must not have any cards of the same color in play. Given that my Uno deck is a fairly recent version, I'm wondering if older versions did have that rule? Or maybe it was just a house rule. If so, is that a common house rule? Or maybe it just stemmed from the need to not have the current color in your hand...