The final colour of an asteroids indicates how closely it comes to the inner solar system.
Earth Crossers are RedNotice now the pattern of discovery follows the Earth around its orbit, most discoveries are made in the region directly opposite the Sun. You'll also notice some clusters of discoveries on the line between Earth and Jupiter, these are the result of surveys looking for Jovian moons. Similar clusters of discoveries can be tied to the other outer planets, but those are not visible in this video.
Earth Approachers (Perihelion less than 1.3AU) are Yellow
All Others are Green
As the video moves into the mid 1990's we see much higher discovery rates as automated sky scanning systems come online. Most of the surveys are imaging the sky directly opposite the sun and you'll see a region of high discovery rates aligned in this manner.
At the beginning of 2010 a new discovery pattern becomes evident, with discovery zones in a line perpendicular to the Sun-Earth vector. These new observations are the result of the WISE (Widefield Infrared Survey Explorer) which is a space mission that's tasked with imaging the entire sky in infrared wavelengths.
The scale of the video at 1080P resolution is roughly 1million kilometers per pixel, and each second of video corresponds to 60 days.
Currently we have observed over half a million minor planets, and the discovery rates show no sign that we're running out of undiscovered objects, scientific estimates suggest that there are about a billion asteroids larger than 100metres (about the size of a football field) .