I find some of the tooltips for comparing gear a little inconsistent.
On the left you'll see that the new harvesting axe has higher logging than my currently equipped axe, but shows a red -40.41 when in fact it's an upgrade of +40.41 and should be green.
The right image where my equipped mail armor which has better resistances and lower sprint efficiency is displaying the formatting as expected.
The Tunic resistance values are red and negative indicating that it's a downgrade, while the sprint efficiency is showing green because it's an upgrade for that attribute.
Another note, I personally find having the sprint efficiency as an inverse value not very intuitive. I tend to think of the term "Sprint Efficiency" as higher values are more desirable than less. However, this tooltip is indicating that a mail armor with sprint efficiency 1.0 is not as effective as the Tunic with 0.5 sprint efficiency.