Which colour to choose for ‘updated’ field?

I'm designing a user interface, which will contain fields that the user can edit.

Each field can have 4 states:

• Unchanged (field has the same value).
• Added (field has a value, where it didn't before).
• Deleted (field used to have a value, and now it doesn't).
• Edited (field has different value to before).

I have decided that each state will affect the colour of the field, for example:

Unchanged

Added

Deleted

I can't figure out which colour should be used for the 'edited' fields. I don't think yellow would work, as it is hard to see on a light background, and may convey the wrong message.

I'm a programmer, not a designer. So is there a colour that is normally used for 'changed'? Any suggestions or answers would be much appreciated!

(Regarding people with colour blindness, this is only a slight visual cue, the actual information on what has been changed will also be available in a database, this is just to aid the team currently working on this form to help make their job easier).