A broad weak absorption in the near infrared is at 740 nm.
This red colour was due to the presence of tetraiodonickelate.
[1] Bis(triphenylmethylarsonium) tetraiodoronickelate [(C6H5)3CH3As]2[NiI4][4] is red in colour.
The red flakes that precipitate must be filtered before the alcohol cools, else the compound decomposes.
[1] Bis(tetraethylammonium) tetraiodonickelate [(C2H5)4N]2[NiI4] has a molecular weight of 826.8135 and a CAS number of 13927-28-1.