How to get the last value from multiple checkbox?

This my checkbox elements:

<input type="checkbox" name="colors" value="blue" /> Blue <br/>
<input type="checkbox" name="colors" value="green" /> Green<br/>
<input type="checkbox" name="colors" value="yellow" /> Yellow<br/>

How can i get the last value from this multiple checkbox, just clear JS because i have been studying JS and HTML just for 2 days. Thanks.