  We demonstrate possible optical signatures of the Kehagias-Sfetsos naked
singularity spacetimes representing spherically symmetric vacuum solution of
the modified Ho\v{r}ava gravity. In such spacetimes, accretion structures
significantly different from those present in the standard black hole
spacetimes occur due to the "antigravity" effect causing existence of an
internal static sphere surrounded by Keplerian discs. We focus our attention on
the optical effects related to the Keplerian accretion discs, constructing the
optical appearance of the Keplerian discs, the spectral continuum due to their
thermal radiation, and spectral profiled lines generated in the innermost parts
of such discs. The KS naked singularity signature is strongly encoded in the
characteristics of predicted optical effects, especially in the case of the
spectral continuum and spectral lines profiled by the strong gravity of the
spacetimes, due to the region of the vanishing of the angular velocity gradient
influencing the effectivity of the viscosity mechanism. We can conclude that
optical signatures of the Kehagias-Sfetsos naked singularities can be well
distinguished from the signatures of the standard black holes.
