I like to use a Presentation tool to create posters. For the upcoming Central Valley Computer Using Educators Tech Expo I was using Google Presentation to make door signs. The logo for the event had a light yellow color along the bottom. I wanted to extend the bottom of the logo to create a solid line across the slide.
I created a rectangle using the drawing tools but the predetermined colors did not match the bottom of the tree logo. Google allows for custom images but it requires that you know the html code for the color.
The chrome extension eyedropper 
is right next to the address bar in my browser. I was able to click on the icon to pick the yellow color. The eye dropper extension promptly gives me the html code.
Clicking on one of the white squares under the word custom in the color options in Presentation allows me to type in the html code that I received from the color dropper extension.
And my poster or slide is now exactly the way I wanted it.