sRGB The “standard” of the web and most photo finishers. Designed in 1996 by Microsoft and HP sRGB has the smallest spectrum of colors of the primary Color Spaces. sRGB was primarily designed for the computer industry as a way to standardize colors on monitors and printers.
Adobe RGB Designed by Adobe in 1998, attempting to duplicate the spectrum of colors created by the CMYK printing process. Offers a wider range of available colors than sRGB. Adobe created Adobe RGB for the growing computer graphic arts sector, leading to a wide adoption by photographers.
ProPhoto RGB Created by Kodak and approved in 2003, ProPhoto RGB started its life out as ROMM RGB. Designed from the ground up as a Color Space designed to supplicate all the colors visible in Ektachrome slide film, ProPhoto RGB has one of the largest color gamuts out there. Designed by photo experts for photography, ProPhoto duplicates most of the humanly visible colors that occur in the real world, surpassing Adobe RGB by a long shot.
Melissa RGB Another Adobe defined Color Space, but only used inside of Lightroom. Melissa RGB is the Color Space all your RAW files are manipulated in inside Lightroom, as you cannot select another working Color Space. However on export you must select an appropriate Color Space to export to. Melissa RGB utilizes the ProPhoto color spectrum and applies the Gamma curve from sRGB, providing the best of both Color Spaces.
This is from the MPix Pro site:
1. Viewing Environment
Your work environment influences how you see color on your monitor and on printed output. For best results, control the colors and light in your work environment.
View your documents in an environment that provides a consistent light level and color temperature. For example, the color characteristics of sunlight change throughout the day and alter the way colors appear on your screen. If you work in a fluorescent lighting condition, eliminate the blue-green color cast installing D50 (5000° Kelvin) lighting. You can also view printed documents using a D50 light box.
The amount of lighting is important when working with your images. Create a lighting environment conducive to reading a book – not too dark, or too light. If you have the ability to measure your light, the typical light level should be about 55-60 lux.
View your document in a room with neutral-colored walls and ceiling. A room’s color can affect the perception of both monitor color and printed color. The best color for a viewing room is neutral gray. Keep in mind, the color of your clothing reflecting off the glass of the monitor may affect the appearance of colors on the screen.
Remove colorful background patterns on your monitor desktop. Busy or bright patterns surrounding a document interfere with accurate color perception. Set your desktop to display neutral grays only.
View document proofs in the same real-world conditions that your client will view the final print(s). For example, you might want to preview a portrait under incandescent lighting (typical lighting in most homes).
"Rendering Intent - Start with Perceptual. Your other option for inkjet printing purposes is Relative Colorimetric. Rendering intent dictates how Photoshop will deal with out of gamut colors.
Perceptual aims to preserve the visual relationship between colors so they are perceived as natural to the human eye, even though the color values may change. Perceptual is suitable for images with lots of saturated, out-of-gamut colors.
Relative compares the extreme highlight of the source color space to that of the destination color space and shifts all colors accordingly. Out-of-gamut colors shift to the closest reproducible colors in the destination space. Relative preserves more of the original colors in an image than Perceptual."