The palette you're given for displaying photos on the web is called sRGB. When you upload to Photo Finale or Prestige Proofs the photo will be converted to this sRGB color space while viewing on the website, but your original image can be in any color space you choose.
Another popular color space is Adobe RGB, however very few windows-based or mobile-based browsers can display Adobe RGB. When the customer views the image, it is displayed in sRGB. It is possible for a consumer to view Adobe RGB via a browser, but that is only in the Macintosh browser Safari, but only under conditions not normally found in everyday browsing.
Most JPEG files are 8-bit, which means you get 256 reds, 256 blues, and 256 greens whether you use Adobe RGB or sRGB. The difference is the space between colors in Adobe is a bit broader and allows for a broader range of colors. However, there are finer increments of skin tone in using sRGB, for example. But the pure cyan in HP's original logo can only be accurately represented by Adobe RGB, whereas in sRGB, you'd have to pick a substitute color. The best (and shortest) explanation of these trade offs is below:
http://www.cambridgeincolour.com/tutorials/sRGB-AdobeRGB1998.htm
That depends on both the photo and the printer. Most commercial printers only support sRGB. This includes: WHCC, Bay Photo, Mpix, EZ Prints, Shutterfly, Kodak, Fujifilm, Photobox, Costco, Snapfish, etc.,
Since your customers are viewing and previewing the images via a browser or a mobile device, it is best to give them what they see. Very few people aside from high-end color experts notice that photos displayed in web browsers are limited by how many colors they can display.
If you want them to display well on the internet, sRGB is the only choice.
Your camera captures images in RAW. Many high-end cameras give you the choice of converting, in camera, to Adobe RGB or sRGB before saving on a memory card. Sometimes the best workflow is to save your photos in Adobe RGB because it preserves the most colors, and convert to sRGB for the internet.
The problem with that is you get the disadvantages of both color spaces with the advantages of neither.
If sRGB covers the colors of your shots (as it does for weddings, portraits, and most event photography) and your shots are destined for the internet and commercial printers, we recommend they not pass through Adobe RGB first.
The last thing a self-respecting color expert wants is to give up colors. They want monitors and printers that hit every color perfectly, and ICC profiles attached to each image. But the power of the internet is its simplicity. The internet works on TV and TV on the internet. Consumer devices like cell phones and TVs don't know about ICC profiles, and neither do consumer websites like CNN and eBay. They do know sRGB. Fortunately, 99.9% of us think photos look gorgeous on the internet, and it flourishes because of the simplicity of assuming every file is in sRGB.
It is possible in Photo Finale and Prestige Proofs to print via Adobe RGB. To accomplish this, you need to make sure you upload via the Proofing Gallery website, and not allow the customer to crop or render the file. (This only works for prints, not books or other creative products.) So, every print size needs to be the same aspect ratio as you are shooting. If you shoot 2:3 aspect, then your print options need to be the same (4x6,6x9,8x12), etc.
Once the customer renders the image as a card or book, the file will be converted to sRGB.
In addition, the flag “Normalize for sRGB” needs to be turned off in Lab 50.
All this being said, the best practice for a photographer who is displaying images online for printing is to: