The lethal gene of "harlequin" is not present. There is a white spotting characteristic of all canines - both purebred and bezbrodnyh. It occurs in wolves and foxes.
Do not confuse the white patchiness (pegost) with the marble color (merle).
They flew and half-flew for marble.
In white dogs in some breeds of dogs (and cats), color is linked to deafness.
The unusual color of Dalmatians is also burdened by some anomalies. The frequency of appearance of deaf dogs in this breed is significantly higher than in other (single-color and spotted).
From the mating of an individual with a solid color and an individual with a white-spotted color, the probability of producing white-spotted offspring is very high. It is very large. Why am I talking about "probability" - because dogs give birth to fewer descendants than there are variants of the layout of the genetic "patience".
From two individuals with solid color, but having ancestors with a white-spotted color, the probability of birth of white-spotted offspring is very high.
Your white dog (with a solid white color, but spotted skin) has all the possibilities to create white-spotted descendants.

Photo by N.Maslennikova
Dwarf poodle harlequin color Gently Born Tini Tunes