You really cannot tell these two species apart by coloration - way too much variation.
Soft fin ray counts can be used, but there is about 10% overlap with those. Miles tend to have 10 soft dorsal rays and 6 anal fin rays while volitions tend to have 11 and 7.
If you know where the fish came from (not if it is from the Atlantic) Miles are Indian Ocean / Red Sea and volitions are Indonesia eastward. There is probably some range overlap around Malaysia.