IDE writes a red note on bottom of the IDE window.

After a pause with Arduino, I installed 1.8.5 version of the IDE. Then I tested an example for DUE with it. After Verify I got this

Archiving built core (caching) in: C:\Users\LM7\AppData\Local\Temp\arduino_cache_5856\core\core_arduino_sam_arduino_due_x_dbg_2827dcfd51d4742e208ca5016f11e495.a
Sketch uses 54144 bytes (10%) of program storage space. Maximum is 524288 bytes.

Should I be worried, if not, why it is in red.

Regards
LMI1/LM7

Nope, that is not a problem.

The issue of the message being incorrectly shown in red has been fixed for the next IDE release. The message will also only be shown in verbose compilation mode since it's rarely useful information to the average Arduino user:

Everything seems to be managed well

Thank you