I like the glass part. The finish on the metal has been applied and is sealed with some kind of varnish. I think you could just abrade the surface with steel wool or maybe an abrasive pad and then paint it. The easiest way to go would be matte black from a spray can. I did that recently on a ceiling fixture and it looks great.

If the pictured fixtures are brass (and not just painted to resemble brass) you can clean them beautifully with a combination of table salt, flour and white vinegar. Put the salt and flour in a bowl and add enough vinegar to create a paste. Don't make the paste too thick or it will dry too quickly. Rub this paste onto the brass surfaces and leave it in place for a few hours, then wash off. This cleaning method is super easy, inexpensive, effective and less toxic and grimey than using commercial brass cleaners. (I have used commercial brass cleaners and many smell like kerosene and make everything around the article you are cleaning - black !)
The salt acts as a slight scouring agent and the flour is the holding agent for the vinegar which is the actual tarnish remover.

I've found that this site generally has the most thorough instructions on refinishing most anything:

http://www.finishing.com/72/29.shtml

I doubt this is solid brass but it's easy to tell by scraping the fixture in an unobtrusive place and seeing whether it's brass colored or dull gray.

They look solid brass to me. They have a lovely patina that can only come with age, like maybe 100+ years.

Very nice. Leave it alone - I love that patina.

But if you want ot polish brass or bronze to make it shiny, I recommend an acid-based cleaner.

Honestly, just clean them with a soft rag and mineral spirits to remove any loose dirt/oils. Let dry completely. Spray paint your fav color.

If you could - please tell us where you found these, they're awesome!

If it is just "brass coated" you might be able to chemically strip it with oven cleaner and shine up the metal underneath for a chrome effect. I did this with some brass side tables and resold them on craigslist for big money. It is a little labor intensive but worth it- check it out!
http://www.stylenorth.ca/blog/2011/02/strip-brass-with-oven-cleaner/

I feel like you cannot paint these without making them LOOK painted and cheap...Why not just sell on craigslist and buy something more your color?

Or keep the brass because it's the bees knees.

Somethings are are better left alone. Just clean them up. Does a magnet stick to it, then it's brass if not, it's not brass..

oops! correction brass plated holds a magnet, solid brass does not.

I have several living brass( brass without lacquer) fixtures, door handles, etc. Your fixtures look like they have an "aged brass" finish applied to them. Living brass has a much deeper luster.

You might get a good effect with a blackening wax (a car wax rather than a furniture wax in this case, because of the heat from the bulb). It will deepen and enrich the color. On that silly British show where people redid one another's houses...can't remember the name...the designers used blackening furniture wax a lot to bring out relief on things and soften the lines.

Another possibility is spray painting them an oxidized metal base color and then rubbing an appropriate highlight color on the relief (black base with gunmetal highlight, deep copper brown base with copper or blue green highlights, etc.).

if you dislike the look of the brass, use a primer that will let you paint on metal, then try chalk paint (which you can make yourself in any color, recipes all over the internet) and distress it.
I agree that they are outdated. However, considering the trouble and cost of primer, painting, distressing and remember that you'll see them every day if they aren't what u really want, I say go out and buy new lights and sell these.

to see what chalk paint can do for metal, go to
http://elizabethandco.blogspot.tw/2012/03/how-i-make-chalk-paint.html

They don't look like brass to me, more like some kind of antiqued pewter-look metal with a clear finish.

Clean them well, spray with a primer that is meant for smooth surfaces, then paint.

I spray paint brass chandeliers, and have found that an etching primer makes a huge difference for the final coats. I also topcoat with a glossy acrylic finish.

I second Rucy, finishing.com is a great source of information.

Please leave them be--they are lovely as is.