Lupp, thanks for the note. Ultimately, you and I are in agreement. The question then becomes, how to prevent it from happening.
(Slighly off topic)
We don’t know the future, and the force isn’t with me when trying to influence it.
Politics globally should ensure their priority over economism and the related tendency of marginalizing well-considered concepts. Independent of the “system” they seem to fail. It may be another case of the evil GameOfPower. Historic powers also failed in the end…
Anyway: One day everything now actually happening will be part of what preceeded the glorious age to come. “It will be have been good.” We also are successors to failing powers.
Using color to mark up data for significance makes some sense.
Using such coloration as a condition for sort, filtering or summaries is a bad idea, because color is not an exact value.
Color is a visual clue. Vision varies from person to person, depends on lighting situation (white balance and such) and may be perceived differently depending on previous eye exposure. Also, color is a product of 3 or 4 distinct magnitudes (Luminance/hue/saturation, 3 additive primaries or 4 subtractive primaries) which can sometimes yield similar coloration (to our perception) from very different magnitudes.
In other words: Creating a solution which makes sense to the average user is a fairly overwhelming task. Also, because the input is not deterministic, it is not good input for a typical spreadsheet task. With limited developer resources available, this is not likely to be given priority.
Yes, there is a hack, as I have seen mentioned. No, I will not search for it and test it for you. Do a search. You are likely to find ut.
If you must do things the Excel way (be it out of own desire or client demand), at best use Excel.
“color is not an exact value” is not true. On your computer it definitely is very exact (most common is a RGB value).
On your computer it [color] definitely is very exact
The RGB value, its rendering on screen/print (after translation to CMYK) and our perception of it are three contexts which do not have a predetermined, exact congruence. Marking something in red and then searching for red is not likely to succeed, simply because rendering technology and our perception is not able to match the computer’s theoretical color resolution and repeatability.
#B080A7 is certainly an exact value. I maintain that Mauve is not. You may disagree.
I agree that people don’t always perceive colors the same way, absolutely correct. But that is not relevant to the question of being able to sort by color in LibreOffice. We don’t speak to Office (yet) but give it specific commands. For example: put all cells with background color #XXXXX on top. I really don’t understand the aversion in this topic to making this possible 
Of course, it is simple for LibreOffice Calc development, to implement this by a few lines of code, and in fact it’s simple for a user to get the intend ed result based on a helper function. This would not change the fact thate there are 16777216 “different” colors, and no reasonable way to descibe their “degree of similarity” or any kind of “natural order” to a certain level of rationality.
If we start talking of such granular features like put all cells with background color #XXXXX on top any reasonable structure in sheets will be lost, and the next few hundred feature requests will follow.
Find all cells of same CellBackColor as the one having the focus. is OK.
But: Software handles colors by palettes , and palettes aren’t specified by any common standard.
This statement makes no sense to me. “Using such coloration as a condition for sort, filtering or summaries is a bad idea, because color is not an exact value.” In my case I use Format—>Conditional—>Condition—>Cell value—>is duplicate—>Apply Style—>Error to mark cells with duplicate content. What is the point of having a function to set a background color for cells and then say there’s no reason to use the color as a filter or sort function? Having identified all cells containing a specific color I need to somehow copy the rows with cells having that specific color, and only those rows, to another sheet. Manually copying thousands of rows with duplicate content defeats the value of being able to identify them.
Even if Calc had a filter based on cell attributes it couldn’t filter based on conditionally overlaid attributes because they don’t get asigned to the cells but only applied to the cell areas in the view.
This is something you cannot change “just so”.
I hadn’t any Excel at hand for many years now, but I would assume Excel also doesn’t filter based on conditional formatting. That’s for efficiency reasons.
However, I can’t know. Excel seems to not be software, but just a bag of features. This “programming paradigm” has lots of disadvantages, but adding a feature is the one thing that’s rather simple this way.
This is actually exactly what I was looking for in LibreOffice. On a daily basis, I need the ability to give cells a color via conditional formatting, and then sort them based on the color(s) applied. I need to be able to do this quickly, without formulas or programming.
I bought a new license for Microsoft Office which solved my problem.
A new column would have solved your problem better.
I’m done arguing about this. LibreOffice couldn’t do what I wanted, so I bought a product that could.
To me the arguments for not using color are non-sense.
Color is an important feature to any data summary or dashboard. It adds another dimension to the same visual (or cell), so you can summarize the information without additional column. People cannot see colors? So maybe they shouldn’t drive a car either.
The user can change the format or color and mess the calculation? Another non-sense. The user can also delete the auxiliary column. You can protect cells, can’t you?
Generally colors are used over calculated cells, so users will hardly mess them.
A good summary/dashboard will be full of colors to indicate bad or out of target values. Filtering the out-of-target values through their color, which is already there to show they are bad, is a very useful feature, so you don’t need to pollute a summary dashboard with tons of extra columns and user won’t get trouble trying to find where are the auxiliary columns to filter.