[Usability] Adwaita icons for Rhythmbox and Files too similar

[Otso <beiren myopera com>]

Good day,

In my morning haze I was about to open Rhythmbox from sidebar and
clicked the Files instead. I keep those adjacent to each other, and this
has happened before. Their icons look very similar with default Adwaita
icon theme, which I love. Both are boxes of about same height, form and
colour. This is a very small thing, but usability is all about those
small things. 
My vision is close to perfect and I still do that mistake from time to
time when operating quickly, so from usability standpoint the similarity
could be very problematic for those with poor vision or even for people
who just want to start applications from sidebar glasses off.

Regards,
Otso