P.S.: I apologize for directly linking not one but two large animation clips,  
wasn’t really thinking about potential size problems. :(
 
On topic: I love the OC’s colors, very beautiful :3

@Kazapsky  
@Phantom Rider  
Truth is, it really varied between episodes and even between scenes.  
Multiple animation studios were involved.  
Some shots are very nice, and some are very not.  
Here’s a couple of examples of G1 Dream Valley animation and how the ponies usually look:
 
Fizzy making a basket at the start of the movie, her first major appearance:  

 
Fizzy in a later tv episode, doing a cute walk cycle while she’s trying to bubble-levitate a polo ball:  

They were shaped more like this than the FIM ponies. But yeah, 80s cartoon art has its technical limits. But this is one of the best fanart balances between accuracy to the G1 style and the need to look good.
 
http://i674.photobucket.com/albums/vv105/Cessy_Eve/My_20Little20Pony/fizzy.jpg
 
http://img.photobucket.com/albums/v497/RaptorRed/Pony/FG1-Fizzy.png
 
G1 MLP coulda been worse: The worst of it was that outside the first special, every pony was a straight recolor of every other (It’s just that Fizzy’s colors make the one mane and tail style that exists look great.) and it was more error prone. You’ll see how even in that first shot, Fizzy’s head isn’t the same green as her body. In G1, expect multiple noticeable errors in every episode, til noticing them stops making you feel cool.

@Phobia
 
Not really. G1 was done on a shoestring art budget, as were most 80’s cartoons.
 
This has more to do with the artist’s own style than show canon.

Wow! Were the G1 characters really this beautiful?! :D