This work presents the results of a study on the synthesis and characterisation of hydroxyapatite nanoparticles doped with iron ions to create biocompatible pigments in the red spectrum. Using a simple and scalable co-precipitation method, nanoparticles with controlled structural parameters and colorimetric properties were obtained by varying the pH of the medium (8 or 10) and the concentration of dopant ions (5, 10, or 20 at.%). Powder X-ray diffraction, infrared spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were conducted to determine the phase composition, crystallite sizes, and unit cell parameters. A combination of experimental and quantum chemical approaches confirmed the presence of a non-classical nanoparticle growth mechanism—the process of oriented attachment of initial blocks. A methodology for studying colorimetric properties using the CIELAB colour space based on the use of a portable colorimeter was developed. A cosmetic product based on the synthesised nanoparticles in the form of lip balm and eye shadow was created.