Lemon yellow (PY175)
The original pigment with the name lemon yellow is Barium chromate, it has the index name PY31, the pigment is toxic and is no longer used in watercolor paint. Instead, various AZO pigments have taken over the name lemon yellow, the most common is Arylide yellow PY3, which is sometimes called Hansa yellow light and sometimes it is called lemon yellow. This pigment is a little too greenish yellow to be a perfect primary yellow, its lightfastness is good but no more than that, so it’s a little strange that so many manufacturers use it instead of the excellent benzimidazolone (PY175)
Like so many AZO pigments, PY175 is a bit dull, a bit flat. but it fits perfectly in the color wheel for a primary yellow color so it has its place in the watercolor palette, it also has excellent blending properties. It is semi-transparent and staining and is two-toned: it is slightly cooler in thin layers of paint and a little warmer when you paint thick with it.
If you think it is important to have a good primary yellow in your palette, then you should buy this color, it is the perfect primary yellow. I myself almost never use it, only when I have to, e.g. when I paint with French ultramarine and want a reasonably clear green color mix, then it is great to have. But otherwise I prefer several other, more fun, warmer yellow colors.
Since paint manufacturers do not want difficult names for their colors, the paint is never called benzimidazolone yellow but is called something else, not very many manufacturers use PY175 but here are some that I have found:
WINSOR & NEWTON | COTMAN: Lemon yellow PY175
WINSOR & NEWTON: Winsor Lemon PY175
SCHMINCKE | HORADAM: Chromium yellow hue lemon PY175
HOLBEIN: Imadazoline lemon PY175
DANIEL SMITH: Lemon yellow PY175
MAIMERI BLU: Permanent Yellow Lemon PY175
Color index name: PY175
Lightfastness : Excellent
Transparency: Semi-transparent only