Email content strategy

Email content strategy

This is basically a couple of questions about the best practices when it comes to the use of colors as part of the message sent through the email campaign.
1 - Is there a guide or recommendation as to what are the best colors for text/background associated to services and/or products?
2 - Is there a guide or recommendation of colors to use or to avoid based on:
a - age,
b - ethnicity,
c - religion
Thank you