there are some issues in the linear color space managament
1) The color input slot is not consistent.
The color weel and the HEX and HSV tabs show the color values in sRGB space, while the RGB tab shows the color vaues in linear space.
For example, if you set the color to mid-dark red, that is sRGB 0.5 0.5 0.5, you get HEX 80 00 00 HSV 0 1 0.5 and the color weel positioned to pure red in the disk and half bright in the side bar, that are all correct representations of the sRGB mid-dark red values. While the RGB tab shows 0.214 0 0, that is the linear space value.
It would be correct to have an option, perhaps in the user preferences panel, to let the user choose between linear or sRGB input. In general artists used to Painter or Photoshop will find themselves comfortable with sRGB input.
2) The material color values are changed when changing the display color space and/or when importing/exporting objects.
For example, if you set the color to dark red HEX 80 00 00, then switch the display device from sRGB to REC709, the dark red becomes HEX 73 00 00, if you switch the display device to none, the dark red becomes HEX 37 00 00.
Is seems that in blender the color space is not assigned to the material. So that when the user changes the display color space, then the color values change too. This doesn't make sense since if a color is defined in sRGB space, its definition (values) is the same and doesn't change whatever color space the material is displayed to. That is, changing the output device must not change the color values assigned to a material.
It would be correct to assign a color space to the material, so that the material color values don't change when changing the output color space. If the artist assign the dark red in sRGB space 0.5 0 0 value to a material, he/she expects that the value doesn't change when changing the output device.
Also there are issues when exporting objects. For example exporting the dark red HEX 0.5 0 0 to obj gets exported to 0.4 0 0 in the mtl file.
Also there are issues when importing objects. For exampe, if I have an obj with HEX 0.5 0 0 in the mtl, it gets imported as linear value instead of being imported as sRGB value. This again doesn't make sense since the mtl file defines sRGB values and not linear values.
This automatic linear space assumption is applied for every import/export format it is not limited to obj. And this doesn't work since almost every import/export format such as obj 3ds lwo etc have materials defined in sRGB space and not in linear space.
It would be nice to have an option, perhaps in the user preferences panel, to set the default color space used when importing objects.
It is a shame that even in 2.73 the color management system stills a mess. Please please fix it. It is time.