Here's a quote from DPReview: -
"Just like other Nikon digital SLR's the D70 provides three color modes, Mode Ia and IIIa are both mapped to the sRGB color space and so images shot in these modes will look correct immediately and can be used as is. Color mode IIIa has been designed for use for nature and landscape shots, it provides richer greens and a more natural balance of other colors.
Mode II is mapped to the Adobe RGB color space, this provides for a wider color gamut but will require conversion to sRGB for computer monitor output. Many professional photographers and publications have standardized on Adobe RGB, this ability is now expected of almost all digital SLR's. The D70 uses a different filename mask for Adobe RGB images, they begin with "_DSC" instead of the normal "DSC_". They are also now embedded with the Adobe RGB color profile, this means that color space aware applications such as Adobe Photoshop immediately recognize and apply the correct color profile."
Hope that helps...
Cheers,
Bcoolboy