Action after delete button should be:
yes - no
or:
Delete - cancel
Which colors (Red,Green) should be used with buttons?
Which one should be Red and which one should be Green?
This is very much depending on the design ecosystem you're working with within the brand. However, I would suggest the following:
I hope this helps!
I'd suggest Using one of Google's design Principles which goes like
Decide for me but let me have the final say
Take your best guess and act rather than asking first. Too many choices and decisions make people unhappy. Just in case you get it wrong, allow for 'undo'.
Google has implemented this in both of its Android and iOS Gmail app. When you delete something it doesn't ask for your confirmation like "Are you sure ? ". It rather deletes the file (decides for you), and then provides with the option to UNDO(let me have the final say) it . The undo option is pronounced with the help of eye catching colors and is visible for some amount of calculated seconds, enough to realize if you've made a mistake.
This will obviously depends on the system you are currently developing. But based on the normal user perceptions, Yes button should be green and No button should be Red or Neutral.
The Delete button should be of Red Color as it should warn the user before deleting and the Cancel button should be Neutral.