The lines and colors are being driven by this chart –
Training Status and Form – Xert (baronbiosys.com)
The same colors show your current form based on color of your status stars as well as the triangle in the pacer needle which reflects predicted form 24 hours from now.
Related post:
Adding a Form Colour Chart - Site Feedback - Xert Community Forum (xertonline.com)
“Recovery load quantifies how much recovery you need based upon the recent training you’ve been doing.”
Reference:
Training Status and Form – Xert (baronbiosys.com)
Recovery Load – Xert (baronbiosys.com)