Can you mix pink coolant with green coolant?

youre someone i would like advise from. my car doesnt give me too much confidence and i just want it to last atleast a year more after i pay it off then i will replace it with something else. i currently have just less than 3 years of payment left on my car. my girlfriends car her payments are done in 4 months so im not really worried about her car at this point.

if my car is a 2010 mazda3 and i got 123,000 miles on it what are the odds i would need to have my automatic transmission looked at before it fails? i havent done any maintenance on the automatic transmission. i truly just want this car to last me 4 or 5 more years.