Posted on another post - but applies here as well ...
OK - I'm going to wade in with my graphic knowledge do note however that this only works in this specific scenario: color with overlays transparent white or black and only at 5% transparency intervals.
but that seems to be the question asked here ...
So after seeing these workaround methods and not really finding them to be a satisfactory solution ... I use this method:
Select your base color in CMYK values (lets say a nice green because green is a nice color) add the shape in white over the top and set your transparency of the white shape (lets say at 50% because that's in the middle)
So we have our nice green base and our shape looking like a lighter shade of that nice green (lets call that nice pastel green)
To get CMYK values for our nice pastel green we first use our eyedropper tool and click on our background color our base green
now we have that color selected go to the color guide palette - and we see our base color green selected in the color swatch go to the top right of the palette and the color guide options and set the steps to either 10 or 20 (20 is max) that gives you tints of the color from the base through to white or to black in 10% increments or in 5% increments (depending on if you made 10 or 20 steps)
I'm sure I'll get the haters because it won't work for two CMYK colors and blah blah blah, but the OP asked for 60% on white and this is the quickest method that gives you the exact color values
So I hope that helps in this case and if you want 37% transparency consider choosing 35 or 40 because any printing press in the world has 3% tolerance on its ink lay down on the dot so it actually makes no difference.