Steps to reproduce:

1. Go to Monitoring>Latest data
2. Select something (I picked Zabbix server / Zabbix queue)
3. Click graph
4. Set the graph range to something sizable that covers a significant amount of variation

Result:
See screenshot...

Note that the legend only shows a single color: green
Note that there are in fact 4 colors:

• bright green
• green
• pale yellow
• pale red

Expected:
The legend should indicate that light green represents "min", pale red represents max, and that pale yellow is a range between them...