The first rainbow of multilayer spheres is studied, whose profiles of the refractive index are exponential decrease or increase by using generalized Lorentz-Mie theory of multilayer sphere. The results obtained demonstrate that the angle positions of the rainbow of the multilayer sphere is sensitive to the refractive index profile, whether the refractive index exponential decrease or exponential increase. The results are very useful to probe the refractive index, its gradients and temperature of the combustible particle.