My son asked me to make some certificates to give to his students. I said start skype and inkscape. I told him to draw some squares to show me the colours he wanted, then go to the fill dialogue.

His first colour was light blue. I said go to the CMYK tab in the fill dialogue and tell me the values.

He had: C=27,M=27, Y=0, K=11, A=100

I said that gives me a bluish-grey, not a light blue.

I thought these values were absolute. They are not.

How does that figure?? Depends on what?

They are absolute.

But I can tell you C=27, M=27 Y=0 does not give you a blue color, ever.

Cyan is bluish, so this should be the largest number.
(0,0,0) is white.
(27,0,0) is light cyan
To get a light blue you would need something like (60,10,0)
Equal values of C and M will always give you a shade of purple.
Add some K to this vector and the color will move to grey as you add black.

It seems to me that the values you entered match with the color you see. But I suspect you were give the wrong values somehow.

jlinkels

Ok, maybe what we see on the screen is not the same?? Or my son is colour blind? But his wife was there too!

I don't have the solution yet, but I created absolute colors quite often in the way you describe and try to do now. I used the Gimp colour picker to sample an on-screen image, and then used the RGB values in Inkscape. That is absolute color referencing and I can assure you they matched.

I think you son sees the correct color but uses the wrong dialog, or he has selected the wrong object. The quickest path could be that he creates a screen shot including the selcted object and the (docked) fill and stroke dialog. Even in the F&S dialog you can see which color is created if you look at the CMYK slider position. They all point at the selected color.

jlinkels

Yeah, wierd. My son sent me the .svg file he made, 2 squares. One is filled with a grey-blue and one is a darker blue. The CMYK values are the ones I said for his idea of 'light blue'.

Anyway, thanks, I'll print a few then send to him. If he is not happy, he can tell me!

Remember that the device in question must be calibrated, and that you must be using the correct color-profiles for that device. (This is true for any operating system.) You can't just hold a color-meter up to a regular monitor and get an accurate reading. Not unless everything is calibrated and the device is built to do that.

I'd say trust the numbers. People see colors differently and some degree of color blindness/deficiency is actually quite common. Different screens display colors differently unless meticulously calibrated.