Setting vertex color with ob.data.vertex_colors["Col"].data[0].color stores values wrong when I set the color of vertex data with;

ob.data.vertex_colors["Col"].data[0].color = [0.7, 0.5, 0.3]


and then look at the values, they are different

ob.data.vertex_colors["Col"].data[0].color
Color((0.6980392336845398, 0.49803921580314636, 0.2980392277240753))


Why is this not saved properly?
Vertex colours are stored as 8-bit sRGB values. This means that they have a maximum precision of 1/256, but the raw values are also further distorted by the sRGB colourspace translation.