Yes, color can be very arbitrary ,depending on the ambient light. Without a lot of experience and subdued lighting, judging temperature by eye is nearly useless. The magnet will tell you when it is getting near the austinitization temp. You still need to heat it up 100-150F higher than non-magnetic. Also, 15N20 needs a soak time of 10 minutes at temp. You didn't say how you were heating the blade but it may be hard to hold for that long with an uncontrolled heat source, so most folks quench way too soon. This may result in a lower hardness blade, or other problems.
When staring out and using very basic HT equipment, you can't go wrong with 1080/1084.
Yesterday I was doing a demo in an open field and had the forge running at about 2100-2200F. I was working a sword blade and someone commented that the steel didn't look all that hot, and cooled off to black almost instantly. It was plenty hot. In the bright sun you could barely see any red color after it was pulled from the forge. At night , or even in the shade, the same blade would have looked very bright red/yellow and would have had a visible glow for a minute or more.
