"T. Valko" wrote...
Use the Formula Is option and use these formulas:

For Blue:

=AND($AK$2<"",SEARCH($AK$2,"JANMARMAYJULSEPNOV") )

For Green:

=AND($AK$2<"",SEARCH($AK$2,"FEBAPRJUNAUGOCTDEC") )
....

Quibble: these could return false positives for invalid entries in
cell AK2, e.g., if AK2 evaluated to "ARM", it'd be formatted blue.

Alternatives:

blue: =MOD(MONTH($AK$2&"-1"),2)=1

green: =MOD(MONTH($AK$1&"-1"),2)=0