Transparent coating systems were exposed for 48 month to the normal fluorescent light or complete darkness in interior. In defined time intervals, colour changes were measured. The analyses of colour changes showed that the colour of most transparent coating systems changed substantially in 1st up to 3rd month. In most cases the samples became darker and yellowish. The colour of coating systems was changing also in darkness. In almost all cases, the coatings (polyurethanes, natural oils) increased the colour stability of the transparent coating systems. Regarding the time course of colour changes, 4 characteristics groups of time dependent colour changes were identified. By measuring L*, a*, b* colour coordinates and analysing colour changes in the exposure period of 3 months, the coating systems of furniture can be sorted out in 1 of 4 characteristic groups, and the subsequent colour changes of coating systems predicted.