
A fellow artist introduced me to a blog called design seeds where visitors are treated to a steady stream of inspiring color palettes. Each palette is "packaged" beautifully by designer Jessica Cololuca with photography and a row of color chips.
When you find such inspiring color in your online travels, you want to bring it along with you into Adobe Illustrator and let it enliven your work. In Illustrator though, you can hit a speed bump in the process. So, I have a simple tip for those who want to sample color from pixel based images like jpeg and png files.
If you drag an image from an open browser directly into an open Illustrator document, the image file will automatically embed. It's the quick and dirty way to get an image into your file - and for the purposes of sampling color, it's perfectly fine. (To keep your AI file size low, you'll want to delete the reference photos when you're through with them.)
Next, you grab your Eyedropper tool and click on the color in the image you want, just like you would in Photoshop - only, in Illustrator you may come up with a "none" fill on your color panel. How frustrating!

The easiest way to get around this is to hold the shift key as you click with the Eyedropper tool, and the color will appear in your color panel. (Thanks Clayton! my personal PS guru - sometimes he outdoes me in AI too.) Holding shift while using the Eyedropper tool allows you to sample a single color from within a gradient too.
To follow the Adobe Illustrator logic for this problem though, double-click the Eyedropper tool in the Tool Panel to open it's options dialog. If you have "Appearance" checked, then that is the culprit.

When you have Appearance checked in Eyedropper Options you are essentially sampling the no-fill, no-stroke shape that contains the image you are trying to sample. It's what you see when you look at the image in outline mode. The Eyedropper samples that appearance, rather than the pixels. When you uncheck the Appearance box, the Illustrator Eyedropper will sample the color from a photo. This is why I like the shift key trick so much, because I like to leave Appearance checked in the Eyedropper options.
Finally, try holding the mouse button, or the button on your Wacom stylus when using the Eyedropper tool in Illustrator to sample color from other open windows on your screen.
It's always nice to get a little help (and good links) from my friends!