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I have a black and white diagram, and want to change the lines of the diagram into a specific hex color in Photoshop (CC). I've erased the background, which I don't need, and in the hue/saturation have managed to colorize the black. The problem is that I can't find a way to set it as a specific color, as there's only sliders to adjust, and doing it by eye always ends up being different from what I need. Does anyone have any insight into whether or how that's possible to do?

There may be a different and better way entirely, and the method I've used is simply the thing that has got me closest to my goal but could be a dead end. The other color changing tricks I do know (selection tool, masks, and so on) are impracticable for this diagram, which contains dotted lines and lots of other fiddly bits, but as it's all one color (black) I assumed it would be easy to change in one go. It hasn't been created digitally, so I can't adjust the original.

I'm fairly new to photoshop so might be overlooking something, but after a lot of digging I can't work this out. Thanks!

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You can do it with 2 simple steps:

  • Reduce the image color depth mode to 8-bit (Indexed mode)
  • Open the palette and edit the specific palette color element to another one (Image > Mode > Color Table)

Also, there are other modes to work with specific colors (Duotone, Bitmap) https://helpx.adobe.com/photoshop/using/color-modes.html#duotone_mode

  • Thanks for the reply—it seems to already be on 8-bit (when I go to Image > Mode the RGB Color and 8-bit channel are both ticked; I've googled how to reduce in case I need to do something else, but only find reference to this, so assume it's already on 8-bit. If that's wrong and you could clarify the steps to reduce it to 8-bit then that would be great). But when I go to the Mode bar the Color Table is grayed out, so I can't click it. Any thoughts on what to do would be appreciated! – user971522 Dec 10 '18 at 9:25
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1) Convert the image to RGB.

2) Use the Color Sampler Tool to add sampler in key parts of your diagram

enter image description here

3) You can then use a Channel Mixer adjustment layer (or a different one, according to your preference) to make adjustments to the color, while keeping an eye on the resulting values in the Info window.

enter image description here

  • Thanks! This all works to change the color, but I still don't see a way to change it to a specific hex code color. Is there a way to do that via this method? Moving the sliders gives different colors, but it's near impossible (actually impossible?) to use them to get the same red that I'm after. I need to synch the diagram with the other stuff in a color scheme, and the best I can do still looks quite 'off.' – user971522 Dec 10 '18 at 20:41
  • To get a particular hex code 1) Convert the Hex code to RGB values, RGB = Hex - 1 converted to decimal. For example, 44 33 FF is 68R 51G 255B but the easiest way is to go to the color picker and type in the hex code. 2) Make note of the RGB values. 3) Use the method I described in my answer to get to those numbers. – cybernetic.nomad Dec 11 '18 at 12:33

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