When removing expansion tank found orange and green coolant

I have an 2000 with less than 80,000 miles. Decided to replace expansion tank because of: small leak somewhere in system, level indicator broke, and needle gauge sporadic. Green coolant showing in expansion tank. Drained radiator and found green coolant. Couldn't drain engine block so pulled lower hose of ex. tank and orange coolant came out. (I have bought the correct BLUE to put in)



The QUESTION: If both coolants were used shouldn't they mix together?! Does that indicate another problem in the system?

Please advise - I'm stranded with no help in western Alabama

When removing expansion tank found orange and green coolant