Follow button is confusing

Currently when receiving notifications it shows:
or
and when not it shows:

**Goal**
Change to using a notification icon.
use the bell.svg icon
grey when not getting notifications
dt-blue when receiving notifications.
"disabled" when the option can't be changed.

See
https://medium.com/@union_io/swapping-fill-color-on-image-tag-svgs-using-css-filters-fa4818bf7ec6
for how to change a svg fill color
and this link for what filter property to set based on a hex value.
https://codepen.io/sosuke/pen/Pjoqqp