Overdrive Color Combos

Orange Orange = Nothing
Orange Orange Orange etc (minimum 3) = EXP Bonus, keeps stacking with more orange arts
Orange Blue = Overdrive Duration+
Orange Green = Overdrive Duration+
Orange Yellow = Nothing
Orange Purple = TP Bonus

Blue Orange = Nothing
Blue Blue = Nothing
Blue Green = HP Recover
Blue Yellow = Nothing
Blue Purple = Debuff time extended

Green Orange = Double overdrive count bonus
Green Blue = Overdrive duration+
Green Green = Double overdrive count bonus
Green Yellow = Double overdrive count bonus
Green Purple = Double overdrive count bonus

Yellow Orange = Nothing
Yellow Yellow Yellow etc (Minimum 3) = Class EXP Bonus, keeps stacking with more yellow arts
Yellow Blue = Overdrive Duration+
Yellow Green = Overdrive Duration+
Yellow Yellow = Nothing
Yellow Purple = TP Bonus

Purple Orange = Appendage damage up
Purple Blue = Overdrive Duration+
Purple Green = Overdrive Duration+
Purple Yellow = Appendage damage up
Purple Purple = Appendage damage up/TP Bonus