How to achieve multiple emission color on one mesh..? I tried a color ramp node but its not working i also tried to mix two emission shader with mix node but result is not desired.. 

Like in the image
create different material slots and materials (emission shader) for the same mesh 
go to edit mode, select some faces
select a material slot and press "assign" button
(this will assign the material only to selected faces)
(eevee/cycles)