Abstract: An attachment to a dynamic mixhead allows pigment to be fully blended with a specified volumetric portion of a reactive polymer mix immediately prior to its passing through an in-line motionless mixer. The fully pigmented portion of the mix passes into the motionless mixer concurrently with the nonpigmented remainder of the polymer mix, each portion constituting a discrete stream and positioned in a manner facilitating rapid, improved blending. The pigment pre-blending attachment possesses particular utility for partial or incomplete blending applications, wherein striations of color are desired to impart a marbled effect.