You can apply any colour to particles. This is most effective when your particle texture is white. Colour tends to work less well with coloured particles.
Choosing a Base Colour
Click anywhere in the colour square to choose a base colour. A small circle indicates which colour is selected. The colours are more saturated towards the top of the square. The currently selected colour is shown underneath the colour square.
Adjusting the Brightness
Click on the bar on the right to adjust the brightness or tone of the colour. A bar indicates which tone is selected.
Start and End
Colours can have a START and an END value. The start colour will gradually transition to the end colour during the lifetime of the particle. So if you choose red to start and yellow to finish, the colour will change from red through orange to yellow. Click E = S to use the same colour throughout.