From the factory, the coolant is Ethylene glycol with Supplemental Coolant Additive (SCA). This would be green in color.
With this type coolant you need to test (you can buy "test strips" that you dip into the coolant and read the SCA level off the strip) the coolant SCA levels annually and add SCA (usually by changing the coolant filter - which is called a "pre-charged filter"). If the SCA gets too low it the coolant will not protect the cylinder liners and that can result in a ruined engine.
If the coolant is red-orange, it was probably changed to Extended Life Coolant (ELC) which is now recommended by Cat. With ELC there is no need for SCA. And the replacement interval is much longer than with the old ethylene glycol type coolant.
Although if you are not the original owner and don't have complete service records you can't be sure what is in the system now. If a competent diesel shop did the switch to ELC there should be a label on the coolant reservoir. As you can not mix the two types - it requires a full drain and flush to change to the ELC.