You can take a look at this post: Correct way to pass multiple values for same parameter name in GET request
There's no standard for what you are asking for, but you can take an argument as comma-separated values and split them in Java, or something like that. For example:
my.api.com/search?color=black,red,yellow,orange
or
my.api.com/search?color=black&color=red&color=yellow&color=orange
There also is a comment I really like, that says that the first approach (csv) should be used as OR (I want to search either black, either red, either yellow, either orange objects), and the second approach should be used as an AND (I want an object which is black, red, yellow AND orange, all of them). That comment is the following one: "A would suggest using id=a&id=b as boolean AND, and id=a,b as boolean OR. – Alex Skrypnyk May 7 '16 at 5:13" (on the checked answer).