How to make the background plain white while keeping color of red and blue contours? For printing

[Brett5EE9]

I want to print this map without printing the tan/yellow--just the red, blue, and black lines/words. How can I make the background plain white? Thanks!!!

[Conrad_C · Accepted solution]

One quick way to do it:

1. Add a Solid Color layer, click OK without changing anything. 
2. Set the Solid Color layer to the Divide blending mode. 
3. Hide the Solid Color layer so you can see the actual image behind it. 
4. Double-click the Solid Color layer thumbnail to edit it, and sample the color from a point with the worst color cast (most yellow in this case). Click OK. 
5. Make the Solid Color layer visible again. 

For more details on how that works, you can watch this video:

[Brett5EE9]

That worked, thanks!

[Bob_Hallam]

In Camera Raw you can neutralize the highlights and adjust the colors in Color Blending to whatever you like.