This might be a non-answer, but my honest advice for you is:
Don't do it this way.
As you are realizing, this method is really cumbersome and time consuming. It could be scripted, as @joojaa mentions, but custom scripts shouldn't be necessary for such a common task of matching screen colors to print colors.
CMYK colors are not absolute colors. They are a ...
Make a copy of your RGB colors put it in a folder called colors in document. Use only these colors. You can then drag the symbol swatches form one set over to anothers icon and it overwrites the swatch updating all globally assigned colors.
Now in illustrator you can just record an action overwriting one to another. But you could easily just script this ...
I don't know if this is possible inside Inkscape, but if you open the .gpl file in a text editor it's actually readable and easy to edit. Here is an example:
153 153 153 #999999
0 128 0 #008000
211 141 95 #D38D5F
255 0 0 #FF0000
255 127 42 #FF7F2A
The first three columns are the RGB values of the colors. The fourth ...
Set the foreground color to the color you want before implementing the Hue/Saturation adjustment (as an adjustment layer or simply as an adjustment).
By default, the moment you click the Colorize option, the dialog box will default to the foreground color.
Set foreground color
Create new Hue/Saturation Adjustment Layer
The short answer is: No, technically color profiles should take care of this.
This is a complicated subject, so I will only scratch the surface. There are many more thorough explanations on other questions on this site.
The idea behind color management is this:
You have a screen which is suitable for design work and which is correctly color calibrated and ...
Yes, no, it depends.
The neverending question... Have you defined your color profiles?
Sometimes I do not pick a "more saturated" or "brighter" color than the one rendered with the color profile, but I choose one cleaner, achromatic.
Instead of darkening a color with the complementary one I prefer using black... Sometimes.
Your color probably could be ...
Well perhaps. It depends entirely wether you are doing phisically correct blending or not. HSL is just a polar cordinate RGB with the same gamut as said RGB and same nonlinearity of said RGB.
If you would normal mix paint in a bucket then the answer is clearly no. As that would require your monitor to be linear and lose ability to show 8bit per channel ...
Try this. It's simple:
There's a new top layer which is filled with a color picked from your goal image. The sample is taken from a mid-bright place.
The new top layer has blending mode Hue.
If you have the metallic parts as a separate layer, there's no problem to make a selection to delete the unnecessary color and keep the background intact. If your ...
You have not mentioned anything about the color profile.
My usual example:
Take a marker and draw a line on a coated magazine paper, and on a newspaper. The ink value is the same, the color is not.
Leave your color as Pantone, the point of Pantone is that tries to be an "absolute color".
Define a set of color profiles, for example, Swop2, ...
Gimp likely is not aware of the capabilities of the receiving end of the copy/paste so it copies what it has.
Easy work around:
Add a layer below your image
Fill with the default background you need
Some clarifications first.
I am aware that CMYK is a Colour Gamut used for Printing
@User287001 (btw, this user should put a name behind all that knowledge) already said that it is not a gamut.
CMYK is several things.
A. It is a Color model, generally speaking using primary subtractive colors to generate an image based on a light substrate. The K is ...