replace a specific color

[joost]

I like to be able to replace a specific color in my photo with a specific other color. Ideally, be able to use the picker to select the color to be replaced and pick a swatch representing the replacement color and all pixels in the photo are adjusted. Possible?

[MikeA]

I'm new to the program (Windows version). I'm taking an online course in Affinity Publisher and something mentioned in the section on color swatches occurred to me when I read your question. I tried it and it worked—though there might be more efficient ways. There are some times when this fails, and I'm not sure why yet. At any rate, I got this procedure to work some of the time, as a test:

Created a rectangle and assigned a color to it (picked at random).
Duplicated the rectangle (for later testing).
Made sure both rectangles were un-selected (otherwise I might see only a local change and not a global one).
Went to the Swatches tab and from its menu selected Create Palette from Document > As Document Palette.
Once the palette had been created:
Made sure the new palette was selected in the palette tab's drop-down menu.
In the new palette's tab, located and selected the color I wanted to change, right-clicked, and selected Make Global from the context menu.
Then to see if a global color change could be executed:
Double-clicked the color swatch I'd just made into a global swatch. A small color dialog appeared.
For simplicity's sake, selected the HSL Color Wheel from the dialog's drop-down menu.
Picked a color from the wheel.

Result: both rectangles' colors updated immediately. This suggests to me that the same could be done if you select one of the "modes" with sliders, so that you can select precise values.

Now I have to figure out why this sometimes doesn't work. When it fails, there must be some specific procedure I'm doing wrong.

[GarryP]

I think this really depends on what you mean by “replace a specific colour”. How “specific” do you mean?
For example, do you mean ‘all the blue stuff’, or everything that is coloured RGB 0,33,255, or something in between?
You can quickly replace colours across the photo with the Flood Fill Tool by setting “Contiguous” (on the Context Toolbar) OFF but I’m guessing you will want something more ‘refined’.
You can get good results on certain images by using a quick workflow with the Selection Brush, Masks and the Recolour Adjustment, as shown in my attached video, but that really only works on certain types of image (my video is quick, more care will be needed for better results).
If neither of these things is what you want, can you give us an example of the original image and a better description of what you mean by “replace a specific colour”?

[ciprianSmith]

On 3/13/2020 at 10:09 PM, MikeA said:

I'm new to the program (Windows version). I'm taking an online course in Affinity Publisher and something mentioned in the section on color swatches occurred to me when I read your question. I tried it and it worked—though there might be more efficient ways. There are some times when this fails, and I'm not sure why yet. At any rate, I got this procedure to work some of the time, as a test:

Created a rectangle and assigned a color to it (picked at random).
Duplicated the rectangle (for later testing).
Made sure both rectangles were un-selected (otherwise I might see only a local change and not a global one).
Went to the Swatches tab and from its menu selected Create Palette from Document > As Document Palette.
Once the palette had been created:
Made sure the new palette was selected in the palette tab's drop-down menu.
In the new palette's tab, located and selected the color I wanted to change, right-clicked, and selected Make Global from the context menu.
Then to see if a global color change could be executed:
Double-clicked the color swatch I'd just made into a global swatch. A small color dialog appeared.
For simplicity's sake, selected the HSL Color Wheel from the dialog's drop-down menu.
Picked a color from the wheel.

Result: both rectangles' colors updated immediately. This suggests to me that the same could be done if you select one of the "modes" with sliders, so that you can select precise values.

Now I have to figure out why this sometimes doesn't work. When it fails, there must be some specific procedure I'm doing wrong.

I think this sometimes works and doesn't other times, is the shape may not have been duplicated, or first filled with the colour you have now created as a global colour.
A quick example, create three circles, 2 of these are filled with a colour that is set as a global colour, the other circle fill with the same colour, but not by selecting the global colour from the pallet, use the colour picker for example.
Then when you double click on the Global Colour within the pallet, and change the colour, you should see 2 circles change in real time to the new colour, the 1 circle thats the same original colour but not filled with the Global Colour pallet option will not change.