PDF for press yields strange colours for duotone image

[TypoMan23]

I imported a grayscale tiff into ID, coloured it with 2 CMYK colours. Nothing fancy or complex.
But when I export the file for press, it looks green and pink - totally unrelated and wrong. 
On the left is how it looks in Preview, middle: Acrobat Pro, right: PDF opened in Photoshop.

I need the client to sign off and approve the files, but he will be very confused when he sees green and pink instead of blue and yellow.

I cannot figure out what is going on, and I've tried exporting using various different settings. Going around in circles trying to get this sorted...

Any help would be much appreciated, thank you! 🙂

 

[Randy Hagan]

Have you tried creating your duotone in Adobe Photoshop, then pulling in the updated image into InDesign?

Photoshop really has much better tools to create quality duotone images than you'll ever find within InDesign. You can learn more about creating quality duotones with Photoshop through this link.

Hope this helps,

Randy

[BobLevine]

What does 2 CMYK colors mean? And how are you exporting the file? What settings?

[Frans v.d. Geest · Accepted solution]

You give the answer already yourself: the wrong colours are only in Preview (Mac), that is because 'colouring' involves overprint, something Preview can not show. 

[BobLevine]

I missed the Preview part. This is absolutely the cause here.

[rob day]

Hi @TypoMan23 , I can‘t replicate your problem. Try Eporting using the PDF/X-4 preset—I get this with X4 and placing a .PSD grayscale:

Also, Preview is not a reliable PDF viewer—have your client use Acrobat Reader. Also, check your Transparency Blend Space, if this is for Print make sure it is set to CMYK.