Why Only 1 Material that can be sended??

Iam sorry, If this Question was a re post before.....
But i have read in http://yugioh.wikia.com/wiki/Card_Rulings:Rainbow_Neos



With "Elemental Hero Prisma", you cannot reveal "Rainbow Neos" and send "Rainbow Dragon" to the Graveyard. You have to send "Elemental Hero Neos"

This is weird, Why Prisma cannot send Rainbow Dragon as Rainbow Neos's MAterial???
Since Prisma effect are like this :

Once per turn, you can activate this card's effect by revealing 1 Fusion Monster from your Extra Deck and sending 1 of the Fusion Material Monsters listed on that card from your Main Deck to the Graveyard. Until the End Phase, this card's name becomes the name of the monster you sent to the Graveyard.

So why only Neos that can be sended to grave from my deck after i reveal my Rainbow Neos with prisma effect then?

And The Second Question....

I know that Rainbow Neos are including Nomi Fusion Monster that can only be fusion summoned by send the True MAterial (Cannot be substitute with another monster like king of swamp, ect) as its summoned condition, But Can it summonned by sending Phantom Of Chaos from my field after that monster have copied My Rainbow Dragon's name, effect, and even attack with any Fusion Spell Cards?

Thanks for attention bro.... iam really confused with this.....:D
I need help from a Professional and MAster like all of you....

As far as i remember, you cant use Prisma since the TCG version of Rainbow Neos says
"Elemental Hero Neos" + "Rainbow Dragon" or "Rainbow Dark Dragon"
and the OCG version says
Elemental Hero Neos + 1 'Ultimate Gem God' monster.

Even though we play the TCG, it was officially stated that since the other Fusion Material beside Neos isnt defined in the OCG version, you cant use Prisma or any other "substitute" card for Rainbow Dragon or Rainbow Dark Dragon.

PoC can be used in the Rainbow Neos fusion as Rainbow Dragon, since its not a substitute but takes its name.

Nice answer from all.....
Thanks, so i will put that Phantom in my Rainbow Neos deck now......
But One Think..... Is it true that the reason is because the rainbow neos have 2 material and 1 of those material having 2 optional monster......?
Ok, take it easy, so i will not prolong this problem....... thanks everyone....

It has been answered but this is a simple logic: A card's name cant be " 1 Earth Monster" or such, thus preventong Prisma from being "1 Rainbow thingy" Also, you can use a poc copied rainbow.

Also, the Guy that said OCG stuff is Compeletly right. Thats why I can play Falling Down while I control my Summoned Skull, or hats why I cant use Frog the Jam wth other frogs

Question answered, topic locked