There is no single agreed upon “best” or “safest” colour for an airplane. Many larger aircraft operators paint their planes with company brands, logos or themes, while smaller operators will often paint based on their own interests.
Painting a plane with colours that contrast the sky, water and land is the best way to make it more visible. Using brighter colours does not necessarily create more contrast, as colours like silver or orange may not be visible in certain weather conditions. Additionally, black paint has been known to cause composite materials to overheat past their safe temperature limits in hotter conditions. The most important thing to consider is where and when the aircraft will be used, and use that to determine which colours would work best for you.