Sherwin Williams has a Victorian color palette. Go to their website (sherwinwilliams.com) and look for the Historical Colors palette. You might need to go to the Color Visualizer - I can't recall. Have fun.

First, start hanging out at the Old House forum - what a wealth of knowledge there!

Second, think color on top of color - an Eastlake (also often called a Stick Style if there are vertical and horizontal trimboards decorating the exterior walls) could have as many as nine colors on the exterior, but unless you've got the all-out detail I'd probably stop at five! Main body, main trim, roof, major accent, minor accent. Color of the same value (dark/lightness, intensity) as the roof will work best as long as the yellow isn't super pale, but if it's a good medium yellow you've got it made. While earthier tones (although still in sometimes eye-popping combinations!) are more or less most "period", there's no reason at all to avoid using clearer, brighter colors to keep consistency with existing elements like siding and roof, and it does typically appeal more to the modern eye. Believe it or not a light plum/deep lavender would look fantastic with the yellow (my groomer has a yellow Victorian farmhouse with white trim and deep lavender and green accents, just picked my dog up about an hour ago and had to stop to ooh and ah over the color choices). A midtone blue with a little bit of gray to it will also work, goes nicely with yellow and green, and be a bit more sedate as yellow-green-blue are adjacent on the color wheel. A sort of cool darkish red has potential but that can be trickier. Best to use that in smaller accents, like window sashes. Tiny amounts of black also go well, especially if you have any wrought iron or cast iron accents, but if you use too much there's a potential for the "bumblebee effect"! Something like banding on porch posts bracketing another color (either your major accent or a secondary accent color) would be the best place for that IMO.

There are some wonderful books out there to give you inspiration, I've linked a few here. If you can spare the time, popping into a Barnes & Noble or a Borders that has a cafe where you can sit down with a stack of books and an iced tea to look at some pictures is a lovely way to spend an afternoon (especially if it's hot and sticky out!).
Victorian House Designs in Authentic Full Color (a publication of the period, to boot)
America's Painted Ladies
Daughters of Painted Ladies
Authentic Color Schemes for Victorian Houses
Victorian Exterior Decoration
Century of Color: Exterior Decoration for American Buildings, 1820-1920
Exterior Decoration (1885 book intended for a paint counter display!)
Old House Colors
House Colors: Exterior Color by Style of Architecture
Dover Books' Victorian Houses CD-ROM and Book

If you have access to a paint brand called California Paints, they have developed some excellent historically accurate color palettes in association with Historic New England (one of the premier preservation organizations in the country). Paint's excellent quality, too. There's a dealer locator on that website.

Under no circumstances should you use brown as a major accent color IMO. It is a popular color scheme around here but (sorry to be so blunt!) to me the combination of yellow, white, and brown reminds me of the contents of a used toilet, it's just gross. I'm bracketed on both sides by Folk Victorians with this color scheme and it actually sometimes makes me grateful for the dreadfully bland cream-and-white PO chose. LOL I have a millworker's cottage ca. 1900, which we call it "Victorian Lite" as its Eastlake detailing was stripped away and there are some early Arts & Crafts type elements... I daydream about restoring the shingled exterior and polychrome color scheme. Maybe someday.

I would love to see pictures of your house should you wish to post some. I'm sure the Photoshop gurus would be willing to take a crack at it as well, with some suitable buttering-up. ;-)