Color coding Alerts

I am having some issues with a project alert colors.

I am having two cases that starts an alert.

One is if the value is over 40 and one is over 45.

Reaching the 40 value is a really bad thing and reaching 45 is even worse.

The problem is that I cannot use orange for over 40 as it is really important and needs action to be taken immediately.

Currently I use light red and hard red but I am afraid that they do not differentiate well enough.

Any suggestions please ?