Luxol Stainer is used for adding colorant to emulsions to create a variety of shades which is durable and long-lasting.
While scientific tools have been used to match shades on screen to the shades you will see in actual, yet there is likely to be a difference- the shades displayed on this site are indicative and are not precise representations of actual paint colours due to variance in monitor/phone screen calibrations (brightness, contrast, etc) and resolution as well as screen settings.
There may also be variation in the shade which is finally applied on the required surface due to natural and artificial lighting, darkness of the colour, surface condition and surface finish besides many other factors.