Yes, I know Aussies spell it "Colour" but the web is full of US style spelling, so...
The problem with Adobe RGB is that most displays can't show you the colors, so what you get on screen is an approximation, and when you print it's the only time when you will really see more colors.
I would say "if you need to ask, use sRGB." If you shoot RAW, it doesn't matter as you can convert to sRGB or aRGB at will. If you use JPEG, then it's more difficult of a choice- I would say again, if you are printing and you can print proofs or such, then it may be worth looking into. But if you "need to ask" I would say go sRGB.
Excerpts from wikipedia (numbering by moi to aid clarity of reading)
- An RGB color space is any additive color space based on the RGB color model.
- An RGB color space can be easily understood by thinking of it as "all possible colors" that can be made from three colourants for red, green and blue.
- RGB is a convenient color model for computer graphics because the human visual system works in a way that is similar — though not quite identical — to an RGB color space. The most commonly used RGB color spaces are sRGB and Adobe RGB (which has a significantly larger gamut).
- As of 2007, sRGB is by far the most commonly used RGB color space, particularly in consumer grade digital cameras, HD video cameras, computer monitors and HDTVs, because it is considered adequate for most consumer applications. Having all devices use the same color space is convenient in that an image does not need to be converted from one color space to another before being displayed. However, sRGB's limited gamut leaves out many highly saturated colors that can be produced by printers or in film, and thus is not ideal for some high quality applications. The wider gamut Adobe RGB is being built into more medium-grade digital cameras, and is favored by many professional graphic artists for its larger gamut.
- sRGB is a standard RGB (Red Green Blue) color space created cooperatively by HP and Microsoft for use on monitors, printers, and the Internet.
sRGB uses the ITU-R BT.709-5 primaries, the same as are used in studio monitors and HDTV, and a transfer function (gamma curve) typical of CRTs. This specification allows sRGB to be directly displayed on typical monitors, a factor which greatly aided its acceptance.
- The sRGB color space has been endorsed by the W3C, Exif, Intel, Pantone, Corel, and many other industry players, and is well accepted and supported by Free Software such as GIMP, and is used in proprietary and open graphics file formats such as SVG.
- The Adobe RGB color space is an RGB color space developed by Adobe Systems in 1998. It was designed to encompass most of the colors achievable on CMYK color printers, but by using RGB primary colors on a device such as the computer display. The Adobe RGB color space encompasses roughly 50% of the visible colors specified by the Lab color space, improving upon the gamut of the sRGB color space primarily in cyan-greens.
Note: Not all web browsers are colour space aware. Safari and recently Firefox 3 can detect the different picture file metadata but even that can be a problem because the metadata may not be consistent with content.