Minion Enterprise will send alert emails with a darker motif during "Night Mode" hours.  You can configure Night Mode hours in the table dbo.ServerVariables. 

For example, to set "Night Mode" to apply from 9pm to 6am, make the following updates:

UPDATE dbo.ServerVariables SET Value='21' WHERE Name'NightMode Begin';
UPDATE dbo.ServerVariables SET Value='6' WHERE Name'NightMode End';

After this update, ME will apply the Night Mode (dark) theme to alert emails that are sent between 9pm and 6am.

Here's an example of Night Mode: