Abstract: This invention concerns an attachment in and for a signalling lantern in which there are provided coaxial substantially transparent tubular bodies having mutual guide means so as to be movable along their common axis, said tubular bodies being held in support-cum-guide means adapted to be mounted on face (reflector side) of the lamp and rotary means to advance on rotation thereof (said rotary means) in one direction of one or the first tubular body to envelope the light source, such rotation causing retraction of the second tubular body if it already enveloped the light source and uncovering of the latter, while rotation of the rotary means in the other direction causing said first tubular body to retract and uncover the light source and the second tubular body to advance and cover the said light source, each said tubular body or at least that portion of each as will cover the light source being of different color.