Xiaohong touches balls from a bag. She touches 5 balls each time, and there are always 2 of the same color. What is the maximum number of colors of the balls?
小红从一个袋中摸球，她每次摸5个，总有2个颜色相同，那么球的颜色最多有多少种．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<result>4</result>