I also prefer shadowbolt six (Sci-Twi is incredibly different in the movies compared to Twilight mainly that she was extremely greedy in friendship games & was also not altered in personality as midnight sparkle since Demon Shimmer wasn’t changed in personality why would twily’s equivalent be? She also thinks she’s the main character 24/7 in the movies, mainly legend of everfree)

It should have been Lightning.  
@Mrmildock  

 
Rainbow Dash was not replaced (and Derpy is great).

Hence there was a EqG Lightning Dust toy and the Indigo Zap toy looking radically different from her animated counterpart.
 
Is also part of the reason why she isn’t in Dance Magic?
 
Couldn’t they just make Lightning and Indigo twin sisters?

Moltres, Zapdos and Articuno

@Beau Skunky  
A while back I also came to the conclusion that they appeared similar enough that fans simply recolored RD to make Derpy image macros and fan-merchandise and it stuck (one of my own things still on this very booru fell victim to this, though I’ve fixed it since then), even though they weren’t true recolors (like how Lyra and Minuette’s base designs are similar, but not identical). I know you understand this, though.
 
However in the show, there are a few instances from The Last Roundup to Rainbow Falls to Twilight’s Kingdom where it looks like some of RD’s mane symbols were recycled for Derpy:
 
 
 
Not that I agree with these, though.

@Beau Skunky  
Yeah, I guess the term “recolor” is somewhat subjective. I consider Raindrops to be Derpy’s recolor, although Dash’s design shares some similarities. I didn’t notice their difference in hairstyles when I first watched MLP.

@Twily Neutron  
I noticed that (hence why I said “kinda”) though, they do still look a li’l similar, but rarely any fans regard it, because of their hair, and eye differences.
 
Depends on what a “recolor” is to everyone, as everyone have different standards.  
Shadow the Hedgehog doesn’t have the exact same hair/spikes, gloves/shoes, or features as Sonic, (much like Dashie & Derpy’s differences) yet Sonic fans still call him a “recolor.” (Especially, the older ones who despise the character.)  
Yet, I never see characters like Dark Pit (Kid Icarus.) get called that, as well. (Worst he gets is just “SSB clone.”)

@Beau Skunky  
Actually, Dash has a slightly different hairstyle than Derpy, so she isn’t a true recolor. I think it’s more noticeable in EQG though.  
 

@Mrmildock  
She kinda is actually. Surprised that wasn’t an issue with all those anti-recolor types.

@Millennial Dan  
But Derpy is RD recolor, and that’s never complained about.

@Millennial Dan  
agreed.

Explains why she was a bit nicer.

@Ebalosus  
It was distracting anyway. Every time I looked at her, I thought, “Huh, looks like she was originally Lightning Dust.” They should have either left her as such, or come up with an entirely different design.

@Background Pony #A8EF  

This. I mean, one out of five being recognisable from the show would be quite distracting IMHO.

It was obvious, but why did they change it?

@Shepherd  
A principal that should’ve been dead over a millennium ago makes more sense versus a woman who maybe would be ten or fifteen years younger in her AU counterpart? Yeah, no.

@overthepacific  
In a word Yes.

@Mellow91  
And having a thousand+ year old ancient alicorn ruler being a middle-aged school principal does?

I knew it

@Background Pony #61D9  
I actually like the idea of Equestrian Indigo Zap being related to Wind Rider.

@MadBrony  

sounds like a good headcanon

@Mellow91  
Which is why they changed it

I knew it. I frickin’ knew it.
 
Eh, doesn’t matter anymore. After having watched the movie a few times, I’ve taken a liking to Indigo. Not quite LD, not quite RD, but a mesh of the two. Zealously competitive, but not a reckless daredevil.
 
Or maybe it’s just the hair XD

@Sonicrules831  
I am too. I love Lightning Dust but I disagree with her fans hating on Indigo just because they really wanted to see LD’s human counterpart in Friendship Games.
 
Yes, Indigo IS kind of a Lightning Dust recolor, but people need to realize the other four Crystal Prep girls who were rivals to the humane five were also completely-original and not just human counterparts to famous rival/antagonists to the mane six back in Equestria.
 
I’m guessing fans got their hopes up from seeing human-world Suri in the promotional art for the movie and assumed the other minor antagonists would make their grand appearance in human form too. When in reality human Suri was literally shown for a total of six seconds and I don’t remember her getting a speaking role either.
 
I think the writers wanted to create five completely original rivals to the humane five, and there is nothing wrong with that.

I’m cooling with going with Indigo Zap