[paul.fr]

we all know about rainbows, but is it possible to have a snowbow? If yes, would it look the same as a rainbow?

[syhprum]

No....rainbows work because the light is diffracted thru near spherical rain drops this could not happen with snowflakes.
if the snowflakes were hitting a warm layer on the way down, melting to raindrops and then freezing again to hail you could see a rainbow while hail was falling but raindrops never reform into snowflakes.

[another_someone]

But in any case, snow is reflective and rainbows happen because of internal refraction, which implies transparency.  Crystalline ice can be substantially transparent, but not normally spherical.

[DoctorBeaver]

Well, now, hold on boy. I say hold on.

Ice crystals in the upper atmosphere cause those solar halos referred to in Neil's recent post.

[lyner]

Just a point of order; It's REFRACTION when light's path is bent as it goes through the boundary between transparent materials and internal REFLECTION when is 'can't get out of'  a raindrop.
DIFFRACTION is a wave phenomenon more than a  'ray' phenomenon.
Having said that, Diffraction is the daddy of them all,  in as far as diffraction  calculations can be used to tell you what will happen when light hits anything.  But that's just doing things the hard way, usually.