As a general rule, gray always has a knockout effect on the underlying inks, regardless of the Gray object’s type or OPM mode.
Therefor, the Force Overprint for all separations will change the color space to a Black separation, and turn on Fill Overprint using Overprint Mode OPM1.
The result will be that the gray object will no longer knock out the background colors.
| Regular overprint | Force Overprint on all separations | |
|---|---|---|
| Preview |
|
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| Magenta plate |
 |
 |
| Yellow plate |
 |
 |
| Black plate |
 |
 |
| Resulting color in the intersection |
 C: 0 % M: 0 % Y: 0 % K: 60 % |
 C: 0 % M: 100 % Y: 100 % K: 60 % |