Ethylene Glycol is the base for most engine coolants and has nothing to do with what the coolant type is. Propylene Glycol is also used for environmental reasons. When it is used the name usually has PG in it somewhere if it's an aftermarket brand. OE branded stuff (aka Bobcat Coolant) might not mention it.
Color means nothing but most green coolants are IAT (inorganic acid technology) which use large amounts of silicates and nitrites for protection. These are a couple of the SCAs that need to be tested for an added back into the system since they deplete rapidly. Not all IATs come pre charged with SCAs either. IAT coolants prevent corrosion and cavitation by forming a physical barrier on components, this protects well but causes issues in newer hotter running engines. Silicate dropout (gel) can also be an issue in things like EGR coolers. Conventional IATs can work just fine in most older engines provided the coolant is tested regularly and SCAs are added as needed either via liquid form or through use of a filter pre charged with them. The reason you see scaling is likely due to the phosphates in many of them combined with hard water. Most of the Extended life coolants are phosphate free.
The most common ELC coolants found in trucks are all OAT (Organic Acid Technology) either with (NOAT) or without (OAT NF) Nitrites. Color means nothing but of the main brands you see for trucks usually the NOATs are reddish and the OAT NFs are yellow which is not to be confused with HOAT (Hybrid Organic Acid Technology) "all makes and models" coolant which is also generally yellow. A big reason to not base things off color. OATs are Silicate and phosphate free among others. In simple terms they work by attacking the issue as needed versus just laying down a protective layer. The additives do not deplete rapidly like IATs. Most OATs are much more friendly to aluminum and high heat engines. Nitrite is still added to many because of its role in protecting against liner cavitation. However this is changing because the testing that has been done shows that OATs alone protect against liner cavitation as well, and nitrites do not always play well with aluminum at high temps. For this reason many new engines specify OAT NF. Nearly every engine from Europe requires it, Daimler, Volvo, Navistar, Iveco/Fiat, etc. OAT NFs are rated for slightly shorter intervals, 600k/6yr versus 750k/8yr is what some brands show.