I just did a "minimal" install of Ubuntu Desktop 18.04 and everything's working well for the most part.
However, after installing Gnome Calendar and Contacts, they only have generic Gnome application icons (looks like a purple diamond with a gear inside). Other apps I have installed, such as Evolution, correctly display their icons.
I assume I'm missing a set of icons or perhaps some part of a theme, but I'm not very familiar with how this works, so I'm not clear on what I need to install.
Thanks for any pointers.