Read/unread message (mail) icons are very similar and have equal contrast

[intelfx]

Environment

• Distribution (version): Arch
• Desktop environment: GNOME
• Installing method: Arch package extra/papirus-icon-theme
• App name (version): Evolution (and likely others)

Issue description

The icons Evolution uses for "read email" and "unread email" have same contrast and very similar shapes, making it very difficult to visually distinguish.

Screenshots

Can you tell which mails are read and which are unread within 2 seconds?

Compare Adwaita icons:

Suggestions

As a stop-gap solution, perhaps just swap the "read" message icons between -dark and -light?