I believe this type of project is referred to as geo-engineering, which is a bit more controversial as it's typically assumed that the side effects are somewhat unknown.
They're targeting a pilot within the next 5 years on a single beach, which should help towards figuring what side effects exist.
They also note there exist naturally occurring green sand beaches (https://en.m.wikipedia.org/wiki/Papakolea_Beach), though those are tourist spots and probably haven't been deeply studied.
