This is an element I use when I'm running games. You may find it useful, in which case feel free to steal it, or you might find it to be worthless crap.

Trade Designations, which are sometimes shortened to just "Designation", "TD", or "Rainbow Codes" (the latter often somewhat pejoratively) are indicators of a planet's assessment by the Trade Consortium, which attempts (without much success) to be the sole voice of various traders/etc. However, people do put weight on the Trade Designations as generally valid.

The primary trade designations:

Grey: Planets of little trade interest. Empty rocks, uninhabited worlds, inhabited worlds that produce no useful goods, and various other planets. Note that this does not necessarily mean a safe planet. A floating ball of molten rock is likely to have a Grey designation, notwithstanding that it'd be hostile to life. Taranis 3, an uninhabited world without atmosphere, is an example Grey-designated planet.

Green: Green designated worlds are considered safe, and friendly for traders. There is no guarantee of making a profit on a green-designated world, however (and often the markets are at their most cutthroat on these planets, and margins can be razor-thin). Safe is also a highly relative term. Note also that Green-designated worlds are not necessarily pleasant or safe places to live, and can in fact be quite horrible to their own citizenry. Obol (detailed here: https://www.reddit.com/r/SWN/comments/o90qzt/planet_profile_obol/) is a Green designated world, although with a cautionary flag.

Yellow: Yellow designated worlds are flagged as places to exercise caution. They may be wracked by violent civil wars, or engaged in armed conflict with other systems or planets. They may have Byzantine laws that put traders at risk, such as unusual contraband policies. Faust, which has been locked in a centuries-long civil war between its two major factions, is a Yellow designated world.

Red: Red designated worlds are essentially those deemed too dangerous or hostile for trade. This does occasionally provide for great opportunities to achieve massive profits... at massive risk. Anubis, a world that has been taken over by an unbraked AI hostile to human visitors, is a Red designated world.

Black: A Black designated world is a Banned world. Visits to Black-designated worlds are forbidden, and those who violate this will find themselves barred from most civilized planets. Tian Ji, a planet run by immortal rulers who rely on ghoul immortality technology to sustain themselves, is a Black designated planet because their primary import is slaves to break down into organs, and because they have been known to steal ships and go on covert raids to kidnap victims.

Blue: Blue designated planets are Closed planets. They're not forbidden in the way that Black designated planets are, but they are not open to visitors. A Blue designated planet may have strictly closed borders, or be under a quarantine or military blockade. Sometimes systems will be Black-Blue, indicating the worst of both worlds: A blockade or quarantine around a banned planet (for example, one that has been the victim of a highly contagious Maltech weapon). The Kara-Morasko Orbital Platform is a Blue designated site, as access is strictly controlled.

Orange: Orange designated worlds are for those that do not fit into easy categorizations. They are the "other" worlds that often have strong cautionary notes. Caurus is an Orange-designated world, as they are fairly safe to deal with in most regards, but have a particular hatred for Joyco Foods Interstellar, and will react with extreme violence towards their representatives (or anyone trying to sell their branded goods).