Unity has something call materials, you can add this one to the object and in that material has several options and one of the several options is one that says transparent and inside that one are more so you put cotout and inside there you put soft endge unlit and in the base alpha cutoff you put more opacity or less, and to answer the another question is very simple only in the material of the object is something that give you the option of change the main color and textures to.