An LED signal lamp (100) comprises: a housing (102), at least one LED excitation source (108) operable to emit excitation radiation of a first wavelength range (blue light), at least one phosphor material (114) for converting at least a part of the excitation radiation to radiation of a second wavelength range and a substantially transparent cover (104) provided on the housing opening. In one arrangement the excitation source (LED chip) incorporates the phosphor material. Alternatively, the phosphor can be provided remote to the excitation source such as for example on a transparent substrate which is disposed between the excitation source and transparent cover. In other arrangements, the phosphor is provided on the transparent cover or other optical components as a layer on a surface of the cover or incorporated within the cover/optical component material.