Two ways to go about this ... sending either the bits & pieces used, or complete files. Your choice.
Just the used bits
Select all on a flattened timeline, excluding graphics! ... and do a render & replace to something like ProRes422 or if you've got "really big good files" to begin with, ProRes444. Found in the Quicktime "Format" option.
Check to include handles, so you cover any transitions that wipe between frames. Perhaps enough for a full second each side of the cut.
Send those files, the flattened mp4/H.264 file of the sequence, and an EDL to the colorist. With the sequence selected, File/Export/EDL.
Check with the colorist, but you'll probably want original file names (unless you gave them a different name in Premiere), Include Transitions ... but maybe not much else selected.
That way the colorist can take the media, the EDL, and the reference mp4, put the reference on V2, use the EDL to put the clips on V1, and check between V1 and reference on V2 to make sure they have everything properly conformed.
They do their work, export out replacement clips ... which you then use.
By: selecting all the used clips in the project panel, "offline", then Locate ... navigating to the replacement clips from the colorist.
The Everything process
Export the 'reference' H.264.mp4 file of the flattened sequence, again, without graphics ... export the EDL, and copy all the original files to a folder, with the mp4 and EDL also in there.
Deliver that to the colorist.
Simplest process
Export the sequence to mp4 as above, and copy the original files to the same folder. Let the colorist sort things out. Which can work if there's not that many clips. But if you've got a couple hundred clips, with a lot of cuts ... that's a bit of a mess to work.