So here's a Photoshop technique for making them pop using Color Dodge in Blend Mode.
Let's start with the original image above. I haven't adjusted or touched it up in any way, so it has many issues. We're going to focus just on the eyes, though. Being dark, they were especially vulnerable to turning dull on our overcast day.
After you make a new layer, select both eyes. I'm going to do just one eye so we can compare.
After you've selected the eye, you'll want to smooth and feather is slightly. There's a "Refine Edge" button near the top of your screen for this dialogue box.
Then copy it into a new layer. On that layer, set the Blend Mode to Color Dodge.
In most cases the result is extreme and you have to pull the transparency down to between 10%-30%; in rare cases you'll need to boost the effect by duplicating the layer. The final result should be subtle but noticeable in comparison:
See the slight boost in color and vibrance? This is much closer to how she was in person.