Petroleum belongs to Shani (Saturn), so oil company pumps were blue. A major company opened its pumps in green instead; they ran for two to three years and then stayed closed for about nine to ten years. After blue was mixed into the colour scheme on consultation, the pumps were relaunched and began running.
Finance belongs to Budh (Mercury), so CAs and accountants use green ink. Doctors wear green or blue so that Mercury, the planet of intellect, keeps the mind alert during operations; green also nullifies infrared rays and bad energies, which is why hospitals use green, pista, white and blue. Lawyers choose black for the same reason: even clothes and pen ink work as interior vastu.