An apparatus for providing visual signals relating to a plurality of laboratory sample carriers, the apparatus comprising: a tray for holding a plurality of laboratory sample carriers wherein each sample carrier displays an identification code, the tray having a plurality of carrier bays wherein each carrier bay is arranged to receive one laboratory sample carrier; a tray support for holding the tray; a digital camera mounted with respect to the tray for taking a digital image of at least part of the tray, wherein the digital camera is connected to the tray support by a camera mount so that the digital camera is located to be able to take the digital image of a said tray held by the tray support; a visual signal emitting device comprising at least one light projector for illuminating a region associated with each carrier bay and selectively illuminating each region in different colours (39a, 39b); and a processing device operatively connected to the digital camera and to the at least one light projector, characterized in that the at least one light projector is attached to the camera mount adjacent the digital camera; and the processing device is configured to process the digital image and read the laboratory sample carrier identification codes in the image, the processing device being configured to activate the at least one light projector to illuminate a region of the tray associated with each occupied carrier bay that appeared in the image, wherein the colour that each said region illuminated by the at least one light projector is determined by the sample carrier identification code read by the processing device from a corresponding carrier bay part of the processed image. a tray for holding a plurality of laboratory sample carriers wherein each sample carrier displays an identification code, the tray having a plurality of carrier bays wherein each carrier bay is arranged to receive one laboratory sample carrier; a tray support for holding the tray; a digital camera mounted with respect to the tray for taking a digital image of at least part of the tray, wherein the digital camera is connected to the tray support by a camera mount so that the digital camera is located to be able to take the digital image of a said tray held by the tray support; a visual signal emitting device comprising at least one light projector for illuminating a region associated with each carrier bay and selectively illuminating each region in different colours (39a, 39b); and a processing device operatively connected to the digital camera and to the at least one light projector, characterized in that the at least one light projector is attached to the camera mount adjacent the digital camera; and the processing device is configured to process the digital image and read the laboratory sample carrier identification codes in the image, the processing device being configured to activate the at least one light projector to illuminate a region of the tray associated with each occupied carrier bay that appeared in the image, wherein the colour that each said region illuminated by the at least one light projector is determined by the sample carrier identification code read by the processing device from a corresponding carrier bay part of the processed image.