There are so many KitchenAid Artisan KSM150 models on the market, are there any difference between them?

As far as I know, they are mechanically the same, the difference are the attachment and color.
Commonly, the last two letters represent color, such as “ER” stands for Empire Red; the other letters before these letters and after the 150 represent the included accessories, such as “FE” means the Flex Edge Beater packages.
Check Kitchenaid KSM150 Price at Amazon
For example,
- all the KSM150FE models come with (1) 5 Quart Stainless Steel Bowl, (1) Coated Flat Beater, (1) Coated Dough Hook, (1) 6-Wire Whip, (1) Flex Edge Beater
(This model DOES NOT include a Pouring Shield)
The KSM150FEAQ is Aqua Sky, KSM150FECU is Contour Silver, KSM150FEER is Empire Red, KSM150FEQG is Liquid Graphite, KSM150FEOB is Onyx Black.
- all the KSM150FB models come with
(1) 5 Quart Stainless Steel Bowl, (1) Coated Flat Beater, (1) Coated Dough Hook, (1) 6-Wire Whip, (1) Pouring Shield, (1) Slicer/shredder housing, (1) Slicing Blade, (1) Coarse Shredding Blade, (1) Medium Shredding Blade, (1) 2-in-1 Food Pusher
KSM150FBCU is Contour Silver, KSM150FBAQ is Aqua Sky, KSM150FBER is Empire Red.
- all the KSM150TB models come with
(1) 5 Quart Stainless Steel Bowl, (1) 3 Quart Stainless Steel Bowl, (1) Coated Flat Beater, (1) Coated Dough Hook, (1) 6-Wire Whip, (1) Pouring Shield
KSM150TBAQ is Aqua Sky, KSM150TBCU is Contour Silver, KSM150FBER is Empire Red.
-
The KSM150GBQ models comes with
(1) 5 Quart Stainless Steel Bowl, (1) Coated Flat Beater, (1) Coated Dough Hook, (1) 6-Wire Whip, (1) Pouring Shield, (1) Food Grinder Attachment (1) Fine Grinding Plate, (1) Coarse Grinding Plate, (1) Food PusherPusher.
KSM150GBQTZ is Toffee Delight, KSM150GBQCU is Contour Silver, KSM150GBQER is Empire Red, KSM150GBQFW is Matte White, KSM150GBQOB is Onyx Black.
Check Kitchenaid KSM150 Price at Amazon
- all the KSM150PS models come with (1) 5 Quart Stainless Steel Bowl, (1) Coated Flat Beater, (1) Coated Dough Hook, (1) 6-Wire Whip, (1) Pouring Shield.
The KSM150PSSM is Silver Metallic and the KSM150PSER is Empire Red.
There are also dozens of other colors available:
KSM150PSAC is Almond Cream
KSM150PSAP is Apple Cider
KSM150PSAQ is Aqua Sky
KSM150PSBF is Orange Sorbet
KSM150PSBK is Cast Iron Black
KSM150PSBL is Bayleaf
KSM150PSBM is Black Matte
KSM150PSBS is Blue Steel
KSM150PSBU is Cobalt Blue
KSM150PSBV is Matte Black Violet
KSM150PSBW is Blue Willow
KSM150PSBX is Bordeaux
KSM150PSBY is Boysenberry
KSM150PSCB is Cranberry
KSM150PSCE is Copper Pearl
KSM150PSCG is Canopy Green
KSM150PSCL is Crystal Blue
KSM150PSCO is Cornflower Blue
KSM150PSCU is Contour Silver
KSM150PSCV is Caviar
KSM150PSDR is Matte Dried Rose
KSM150PSES is Espresso
KSM150PSFB is French Blue
KSM150PSFG is Matte Gray
KSM150PSFW is Matte White
KSM150PSGA is Green Apple
KSM150PSGC is Gloss Cinnamon
KSM150PSGD is Grenadine
KSM150PSGG is Grass Green
KSM150PSGP is Grape
KSM150PSGR is Imperial Grey
KSM150PSGU is Guava Glaze
KSM150PSIB is Ink Blue
KSM150PSIC is Ice
KSM150PSKG is Kyoto Glow
KSM150PSLR is Lavender Cream
KSM150PSMC is Metallic Chrome
KSM150PSMH is Milkshake
KSM150PSMR is Meringue
KSM150PSMS is Medallion Silver
KSM150PSMY is Majestic Yellow
KSM150PSOB is Onyx Black
KSM150PSON is Ocean Drive
KSM150PSPE is Pear
KSM150PSPH is Bird of Paradise
KSM150PSPK is Pink
KSM150PSPM is Pearl Metallic
KSM150PSPN is Persimmon
KSM150PSPT is Pistachio
KSM150PSQG is Graphite
KSM150PSTB is Twilight Blue
You can read more KitchenAid tilt head and bowl lift stand mixers comparison here.