declare @a varchar(10)
set @a='2'--黑色
select * from tb where charindex(','+@a+',',','+ colorID+',')>0

------解决方案--------------------
下面的方法肯定行用Contains方法：
C# code

 String str = "1,2,3,4,5";//你数据库中查询出的colorID字段
        String temp=","+str+",";
        int i = 2;
        int j = 6; 
        bool b1=str.Contains(","+i+",");//包含2返回true；
        bool b2=str.Contains(","+j+",");//不包含6返回false
        Response.Write(b1+"     "+b2);

------解决方案--------------------
探讨

SQL code
select * from t1,t2 where t1.Id = t2.colorId and t2.colorId = 2 

select * from t2 where colorId in (select Id from t1 where name='黑色')