Who will have the blue Soul mode in Deltarune, and will it be any different?
Most of the other soul modes have been upgraded from Undertale as followed:
Yellow : Charge Shot Added
Green : Extra Sides To Block Added
Purple : Lines Are Used Differently (bomb attack and final date)
Red : Probably Same (Maybe The Light Effect Counts?)
BLUE : Double Jump? More Gravity uses?
Aqua : I have No idea man
I’ve seen a few fangames with blue soul modes, and they mainly seemed to use a ground pound type attack
But I think it’d be cool if it had some kind of manual gravity control ability
what if the bullet board grows more sides so we have more gravity to go off of
or what if it literally just becomes geo dash
I'd like to mention that orange gets a dash ability, and judging by the Sans fight that likely wouldn't've been the case if the orange soul was in Undertale.
I'm considering the dash ability to be a Deltarune addition for this reason.
Blue soul will probably get an active ability, I'm predicting the summoning of platforms that use up TP.
Most fangames that expand on the blue soul add double/triple jump or ground pound or even both
Deltarune: The Upper Hand intensifies
I like those double jump and ground pound ideas. lt would still make sense too
So basically orange but down
Blue and orange are opposite colors
But orange is right, not up
I'd like to imagine that, like purple, blue mode would get environmental differences rather than control differences. Imagine attacks that have different states of gravity on different parts of the playable zone like some Mario Galaxy gameplay.
I also like to think that Chapter 3's secret boss counts as the aqua soul mode, because you play as an aqua-colored character, doing a gimmick that aligns with the patience trait, in a secret boss battle.
Following this logic the platforming in C5 could be the blue mode and were not getting anything new from Toby
no it doesn't count because you're not blue 
kris is blue haha
rory nite?
which is not used in the fight
son? you play as Kris almost the entire game
and just because Kris is aqua-coloured doesn't mean their soul is aqua
hold breath is optional though. you need to go into the act menu to see it.
debatedly the least secret of them all
No the secret one! The shadow mantle!
ERAM has a gimmick??
yes you use a sword instead of just dodging
I think he's talking about ERAM and HEROSWORD
oh it was already said sry
HERO_SWORD is based on Kris, so that is explained. Besides, it's not a soul.
And ERAM isn't a shadow crystal boss...
Well I guess if you wanna not call it a soul mode, then it's not a soul mode.
Every chapter so far has a side quest where you do a secret thing, fight a boss that wasn't part of the main narrative, and earn a shadow crystal. Chapter 3 happens to have the secret boss not give you the shadow crystal directly after beating it, but instead makes it easier for you to earn the shadow crystal. Just cause of that tiny detail, that boss doesn't count?
Also it being a shadow crystal boss isn't relevant to whether or not its mode could count as a soul mode if you stretch.