the answer is in the FAQ for Dodge City
http://www.bang.cz/phpbb2/viewtopic.php?t=121 D10. Does the ability of Apache Kid prevent other players to play Missed! cards of Diamond against his BANGs?
R. No. Apache Kid’s ability applies to cards played by other players only, thus during other players’ turns. Therefore, he is unaffected by about half of the BANG! Cards, by all Indians!, by Conestoga and by some Cat Balou and Panic! played against him. Other cards (General Store, Hideout, weapons etc.) always works normally.
One other interesting thing to note: During Duel, diamond Bangs CAN be used by Apache Kid's opponent. The only card that has to follow the rule of the diamond is the Duel card itself.
Check out the Apache Kid postings under Character Cards.