so you want colors on your parts yeah?
Unfortunately, I think prick colors can only apply to one object. If you want your colors to be saved and turned into an accessory you will have to use textures! Unfortunately, you may have to learn blender for this (or not, but this is the only way I know how) I will try to make this as simple as possible. 
We can use this as the texture since these are the colors you used (if not make your own texture using the colors you used) (make sure to download the image)
What you will need to do is
Download and Open up Blender (any version is fine, I’m using 3.5 so if you want the buttons and stuff to look the same you can also use 3.5)
click anywhere to remove the splash screen. (overlay box with an image on it)
(this
)
and press A on your keyboard and then X and select Delete (we don’t need the default cube)
Go to the top of your screen and click/hover over File > Import > Wavefront (.obj)
locate your .obj file and click Open. This will import your object.
You may or may not be able to see your object in the viewport but that is ok, we will fix it.
With your mouse in the main 3d Viewing space (viewport) press A to select all.
Click once with your Right Mouse Button to open the Object Context Menu. From there go to set Origin > Geometry to Origin.
this should move your object to the middle of the viewport.
with the object selected go to the material Properties tab in the sidebar
and select the yellow dot beside the Base Color.
click Image Texture
then click Open and import the image of the Roblox colors.
Now that we have our texture set up, its time to put the right colors on the right parts
with your object still selected go to the UV Editing tab
you should see your texture on the Left and your object on the right.
If you don’t, click this button and select your image from the list
and for the object, click A to select all and go to View > Frame selected
make sure your settings at the top left of your screen look like this
go to the side that has the object and Press A again in case you deselected anything and go to UV > Unwrap
Press Ctr + I to invert the selection (this should deselect everything)
now with your mouse, hover over the part you want to color, Press L to select linked.
go over to the side with the texture on it and press S to scale and press 0. This will turn your UV map into a dot.
Press your Left mouse button to confirm the action. then press G to grab and move the dot to the color you want. Press your left mouse button to confirm the action again.
Repeat this step for all of your other parts.
If you run into any issues Press Ctrl + Z to undo and Ctrl + Shift + Z to redo.
If you want to look around at different sides of your object press the middle mouse button (scroll wheel) and move your mouse.
The left mouse button is to confirm and action. If you want to cancel an action press the Right mouse button
Once you are done go to File > Export > Wavefront (.obj)
Now that you have exported the object, import it back into roblox studio and import the texture.
If you have any problems, or questions or need any help (no matter how silly or frustrating it may seem) Please ask! I will be happy to assist you further!
