Logo files, once complete and approved, should not be changing with any sort of regularity. Once a decade or less, really. There shouldn't ever be a concern about repeated changes to multiple files. If files are changing often you may want to rethink brand continuity and integrity. Once created a logo should really only ever change in order to possibly update a clearly dated appearance. For example Burger King's logo changed once in 20 years. Same for Taco Bell's logo - once in 20 years. Then there's AT&T - 1889, 1900, 1969, 1984, 2000, 2005, 2016 - some changes spawned due to legal issues. Nothing with any sort of regularity.
My Workflow, realizing many client are unaware of the color shifts that can occur.....
- I start all designs with a solid black version for preliminaries and overall design approval.
- Once the forms are approved, I create a greyscale version to indicate possible color breakouts. This may ultimately be for my use only in order to explore possible color breaks. Depending on how savvy and involved the client is I may not seek their approval for the greyscale version.
- Once colors are chosen I'll create a Spot Color version, but will then convert that to an RGB version for color approval from the client. I create the spot version first so I can choose good spot colors. I then convert it to RGB for client approval because RGB is the easiest for a client to view. I would note, I do also check the colors in CMYK to ensure there's no hard shift that's going occur.
- Once the RGB version is approved, I then create the CMYK version for print production.
- Write up the usage guide.
I don't seek client approval for the Spot and CMYK versions. The client approved the RGB colors, it's up to me to ensure I match those colors as accurately as possible for the CMYK/Spot versions. The client ultimately approves just 2 files for any logo project - the forms in solid black, then the color in RGB.
I end up with 5 files - black, greyscale, RGB, CMYK, Spot. These are then broken out into formats/sizes to create a "deliverable package" for the client. I retain the 5 base files in .ai format for future projects and place them a directory of logos. All the various formats/sizes are archived with the original logo project files and really never touched again unless I need to restore from a backup.
Moving forward I will merely chose the files I need from the 5 base files depending upon what any future project requires.
If by "assets" you mean collateral materials that have the logo as part of the overall design, then I merely link to one of the 5 base files. You can link to these in, well all the Adobe apps I use. It may not be possible in non-Adobe software. But by linking to them there's still just the same 5 base files. If one of them were to change, all subsequent links would present themselves as needing an update.
I do not think it's possible to maintain a single file for a logo if you care about color. By having these 5 base files all the work has been done. In the future, I do not need to concern myself with color shifts, assuming I chose the correct version for use in a given project. All the effort/work put into creating various color versions is expensed in the logo project and once complete, there should be no reason to alter those 5 base files.
If a single file were used I'd need to alter color each and every time necessary and then check it. Most likely after a period of time, there would end up being multiple variations of the same colors because I may use 50%C one time and 52%C another and 54%C in another, etc. This is compounded if multiple people are working on multiple projects. These variations are what I want to avoid and why I set up the 5 base files from the start.
Even when a client sends me their logo, and it's a single RGB, CMYK, or Spot file, I'll take the time to create these 5 base files for internal use (and build some time into the project cost knowing I'll need to do this). My overall mindset is that I'm a craftsman and this is my profession. It's not extra work or untenable to invest some time in order to ensure all projects moving forward will be the best they can be. Sure I could save some time up front by just using an RGB file for everything. But that's not really doing my best.