I was trying to follow along with the video roughly at the point marked, but I missed that the instructor was on Gradient mode. I tried to match roughly what they put in in HSV in Color mode and got a very different result (both visually and in hex). I then switched over to Gradient mode and got the same results as the instructor. Is there a reason for inconsistency between these two color pickers?
Color: 0.5 H, 0.5 S, 0.5 V = #408080
Gradient: 0.5 H, 0.5 S, 0.5 V = #89BCBC
I'm running Blender 2.93.3, on Mac OS if that matters.
I don't know if there is a reason for this inconsistency, there have been changes to the color spaces in Blender over time.
Nowadays Blender uses linear colors everywhere (even with that Gradient texture) except for the texture paint brushes.
(Maybe they just forgot...). So a RGB of (0.5, 0.5, 0.5) added to itself gives a pure white (which is also how nature works), but human vision is not linear and we are more sensitive to dark than to light and we see that RGB of (0.5, 0.5, 0.5) as lighter than 'halfway between black and white'. If you set the texture paint brush to (0.5, 0.5, 0.5) then that looks like middle grey, but is actually darker, it is in sRGB.
What contributes to the confusion, is the fact that the HEX values (that shouldn't be used anyway) are always (in Blender) given in sRGB, although the RGB and HSV are mostly given in linear color space.
Better to not look at the numbers and just use your eyes.