The industry is finally moving away from this concept. From now on all colors will be talked about in the correct 0 – 1 colors space. The old 0-255 is a hold over from when we could only work in 8 bit colors, we now have better options.
8 bit space :
Real Color Space
Red = 255
Red = 1.0
Green = 0
Green = 0.0
Blue = 255
Blue = 1.0
What is Linear vs sRGB vs Others (yes there are more)
LINEAR () : A color value goes from 0-1 in a linear fashion. If you were to check half way from 0-1 you would get a value of 0.5
sRGB (LINK) : Adjusts the colors to give you more colors in the mid ranges while crunching blacks and white. Mostly for Computer monitors.
rec709 (LINK) : Use for HDTV. Your TV maybe converting this before you see the image