Inside the actual "send sms" box, it would be great to assign colours to different numbers - and then the entire conversation box will be that shade of colour. For example, if I have "Phone 01" assigned to green, the entire conversation box would be a shade of green.

if I have "Phone 02" assigned to red, the entire conversation box would be a shade of red.

This would make it a lot easier to know which virtual phone number is texting out.