Try this...exclude selections in SELECTION1=,SELECTION2=

if( Only({< SELECTION1=,SELECTION2= >} BUKET_MON'I‘HLYTIMETABLE)='less Than 7' , '#66b699',
if( Only({< SELECTION1=,SELECTION2= >} BUKET_MON'I‘HLYTIMETABLE)='7-10','#ffff4d',
if( Only({< SELECTION1=,SELECTION2= >} BUKET_MON'I‘HLYTIMETABLE)='More Than 10', '#ff4d4d'
)))

or with {1} to exclude all selections

if( Only({1} BUKET_MON'I‘HLYTIMETABLE)='less Than 7' , '#66b699',
if( Only({1} BUKET_MON'I‘HLYTIMETABLE)='7-10','#ffff4d',
if( Only({1} BUKET_MON'I‘HLYTIMETABLE)='More Than 10', '#ff4d4d'
)))