Why Most insurance companies them design are same color?

I don’t know whether any one found most insurance companies with a common— Their theme color are Blue and White.(Such as BlueCross BlueShield, United Healthcare, Progressive, Geico, Prudential, WellCare, MetLife, Centene). 

Only few Such as, State Farm uses Red and White. Emblem Health uses Purple and Yellow, Liberty Mutual uses yellow and white/black.

Local only government Medicaid and Medicare companies such as Fidelis Care, MetroPlus, Health First uses Green and White.

Do anyone know why?