Toluidine Red is a semi-opaque, yellowish red pigment with high tinting strength.
Toluidine Red has very good lightfastness.
Toluidine Red is not regarded as toxic.
Toluidine Red or Toluidine Scarlet has been used in inks, textiles, artist materials, and plastics.
Pigment PR4 is an opaque, bright yellowish red pigment with high tinting strength.
Pigment PR4 has good lightfastness, but newer red pigments are considered more permanent and reliable.
Known also as D&C Red No 36, PR4 is used in cosmetic products such as lipsticks. It has been tested for carcinogenic and mutagenic effects in laboratory rats.
Because it is inexpensive and has a long history of use in cosmetic products, Permanent Red PR4 is widely used in artist materials where safety is more important than archival preservation, as in children's art materials.