RGB keyboard

Two challenges await:

You cannot replace just the keyboard -- you must replace the entire palmrest-touchpad-keyboard assembly.  You first need to find one (you can try parts-people.com, but it's highly unlikely Dell will sell you one).

The other challenge is that the entire system must be torn apart to replace the assembly - everything from the screen to the system board needs to be removed.  Since that process doesn't come without risk, note that if the system is under warranty, any ancillary damage won't be covered, and you could well find the warranty voided if you replace the palmrest assembly.

You can view the service manual below to judge whether it's a procedure you're equipped to tackle.

https://www.dell.com/support/home/en-us/product-support/product/g-series-15-5505-laptop/docs

can't i just remove all and then remove the keyboard from the palmrest and replace it with a RGB keyboard ?

Even if you could, it would still require the same disassembly that replacing the palmrest does.  The entire system has to come apart.

On the newer models like this one, the palmrest, keyboard and touchpad are a single, welded-together unit -- you could drill out the plastic welds to remove the keyboard, but since keyboards aren't available as a separate part, you'd still have to buy the entire assembly, and then remove the keyboard and glue it back in place on the original part.

Short answer easier:  NO.

Before making those plans, at least check the photos of the assembly here:

https://www.parts-people.com/index.php?action=search&search=G5+SE+5505+Palmrest

(or rather, inform the shop what you're asking them to do).  

The keyboard is plastic riveted to the palmrest. 

i found a keyboard separately. and i'm not going to disassembly it. i'm going to give it to a computer repair shop i know, where they remove and replace new keyboards. so i'm going to give it to them. i still didn't buy the keyboard. i'll buy it next month and i'll say them to replace the keyboard. if it successfully  fits and works i'll say you. anyways thanks for replying.