Start by drawing the frames. Obviously you can have any shape of frame you want, go mad, but if you leave the lens gap big enough to cover most of the eye I think you get a nicer effect. But that might just be me. I've used the same technique for much smaller frames (on much smaller faces) and it still works.
Right, here's our first palette. The lenses. You can have grey ones or black ones or whatever colour you want, but I'm going for good old brown.
Start by tracing the darkest colours in the lens gap using the darkest shade on your
lens palette. I've only gone over the black here.
Now go over the next darkest colours using the second darkest shade. Don't go colour by colour (as in a different shade to trace over each different colour), I've gone over a couple of colours here.
And again using the third darkest colour. Sensing a pattern yet? Again, I've gone over a few different colours here, don't worry about that.
Keep going using the forth shade of your palette. These steps really are the same, but you can see how much I've gone over with each shade here to give you the idea.
Finish off with the lightest shade. Your first lens is now done. Well done.
Okay, don't just flip the lens to cover the eye unless the base's eyes are actually symmetrical! You can see in the first picture that she's suddenly gone cross-eyed. Have the patience to do it properly, it'll pay off.
Now colour in the frames. This step is pretty self-explanatory. I've gone for white, but it doesn't really matter (though probably best not go for brown otherwise you won't be able to tell the frames from the lenses). Don't forget to add a little shading under the sunglasses.
You can stop there, job done, or you could keep going and have a gradient on the lenses. They're only a few pixels tall, so I'm only having three stages of the gradient. Leave the top one as it is.
Time for an extended palette. It's the same one as before with two more lighter shades. I've recoloured the bits I showed with red and green in the step before to one shade lighter
And now I've done the green bit one shade lighter again, so it's two shades lighter than it was originally. And now you're done :).
