A refractive coating such as a white layer is disposed on a housing component of a portable electronic device. The refractive coating includes pigment particles such as titanium dioxide suspended in a carrier medium such as a polymer matrix. The pigment particles each define air pores or other voids formed by at least partially sintering the pigment particles. A difference in refractive index between the air pores and the pigment particles is greater than that between the carrier medium and the pigment particles. Incident light is refracted at interfaces between the pigment particles and the air pores, increasing light refracted by the refractive coating compared to refractive coatings including pigment particles lacking the air pores.