A solid colorant dispensing unit for dispensing charges of solid spherical colorant particles in a time-controlled way, the dispensing unit having a supply container having a nozzle for dispensing the particles having a number average particle size and a number particle size distribution, wherein a ratio of the standard deviation of the number particle size distribution to the number average particle size of the particles is less than 25%. The nozzle having a dispensing outlet having a diameter taking into account the number average particle size of the particles. The dispensing unit having a control assembly for controlling the dispensing of the charges of the particles by taking into account the properties of the particles and the diameter of the outlet of the nozzle. A tinting machine having the solid colorant dispensing unit.