I found some random book on the internet and there was one problem, it goes like this

"How many different necklaces of six beads can be formed using three reds, twoblues and one green?"

Here is an example of what some of those necklaces would look like for clarification Screenshot by Lightshot

My solution is 12 but i am not too sure in myself so would one of you be so kind to bother to solve this and tell me the solution?