I can make an RGB document, choose a black of say C, M & Y all at 20% K at 100% fill this colour in. Now when running picker on it, Photoshop reverts it to its generic black! I never had this problem with past versions. What is happening now? Any help would be great as I prefer to make backgrounds in RGB mode as colour seems to be better when printing. I used to be able to control the black, but now I'm stumped...

Of course it’s an RGB file just like printing a photograph which is RGB to CMYK, it has to convert. There is no point having the CMYK picker if you can't mimic that colour. In the past you could choose your black paint, and even though in reality it was RGB (because it’s in an RGB file), it would still return to you the correct CMYK value that you chose and mimicked in the first place. PS no longer seems to do that. You choose your false CMYK colour to paint into the document and then when you check it, the values are, well, different. Totally pointless having any colour picker as now you can’t control it. That’s what I'm referring to. The colour you mimic should still return the same values that it mimicked in the first place.

  • 4
    If it's an RGB document, don't specify colors using CMYK - they aren't the same thing.
    – Scott
    Jan 30, 2020 at 1:09
  • thanks Scott. i know its not the same thing its the fact that one could change the values in the past PS versions no problem now you can’t. Why use a RGB doc in the first place - well you can use more filters with richer colour. Filters like lighting effects and creating fire is better in an RGB doc than CMYK (actually can’t use that filer in a CMYK doc) at the same time controlling the black so when printed wouldn’t over saturate and go brownish. Plus in my experience getting the export of the finished file to interpret the RGB to CMYK gives better colour than starting in a CMYK doc
    – mjs
    Jan 30, 2020 at 11:02
  • [In response to edit merged into question:] All that being posted.. View > Proof colors may be way you are after, to show CMYK while still working in RGB.
    – Scott
    Jan 30, 2020 at 19:02
  • Oh ok. Thanks Scott - new to all this trying to find a solution stuff. Will try the proof but its all about the colour mixer/sampler its like mixing paint on your brush but it then changes colour on canvas. PS didn't used to do this - will try a forum
    – mjs
    Jan 30, 2020 at 19:51
  • Welcome to Graphic Design SE. I tried to convert your answers to edit and comments as appropriate, but it’s very difficult to disentangle your stream-of-thought writing, so please feel free to further edit your question. I think your problem is not that this is not a forum, but that your problem is very difficult to grasp. Please try to describe step-by-step what you are doing (including the document settings), what you want to happen, and what happens instead. Finally, please see this FAQ on merging accounts.
    – Wrzlprmft
    Feb 1, 2020 at 11:06

2 Answers 2


Do you know those cubic watermelons?

You can assign a cubic shape to the watermelon... but when you plant a seed, guess what shape you will get.

An RGB file is an RGB file. The information it saves is RGB. When you assign a CMYK value, it is converted to RGB.

The "Generic" black is not a generic black. It is the black that will be generated if you change the mode to CMYK using a specific color profile.

On a PSD file format, you can save different information, for example, some Pantone Channel, but a normal RGB file will save only RGB information.


Here is a short explanation:

First of all you must realize that, unlike in RGB, there can be many different combinations of CMYK values which yields the same perceived color on print. Theoretically it should be sufficient to print with just CMY, but the K (black) has been introduced to keep the total amount of ink down and to make it easier to print black text and strokes. This addition of black makes CMYK more complicated to understand than RGB.

What you experience when selecting CMYK colors in an RGB document is to be expected. What happens is this:

  • You select a CMYK color.
  • Photoshop asks its Working CMYK profile: "How would this CMYK color look if it was printed by a printer which follows your standard?" and converts the color to the absolute color mode Lab.
  • Photoshop then asks the RGB color profile of the document: "How would this absolute color be defined if it were to be shown on a screen which follows your standard?" and the color is converted to RGB.

You use the RGB color in your document. Photoshop doesn't remember the initial CMYK values - only the resulting RGB values. When you later measure that same color the opposite happens:

  • You select an RGB color.
  • Photoshop asks the RGB profile of the document: "How would this color look if it was displayed on a screen which follows your standard" and converts the color to the absolute color mode Lab.
  • Photoshop then asks the Working CMYK profile: "How would this absolute color be defined if it were to be printed by a printer which follows your standard?" and the color is converted to CMYK.

The resulting CMYK color will be defined by a wide range of choices made by the people who made the color profile. Too complicated for me to explain here. The values will probably differ from the values you chose in the first place.

Not the answer you're looking for? Browse other questions tagged or ask your own question.