This paper is based on UBVRIJHKLM magnitudes of about 700 0- and B-type stars obtained from the literature. The mean intrinsic colours have been derived with the aid of two-colour diagrams for 0- and B-type stars of luminosity classes Ia, Iab-Ib-II, III and IV-V. The present results are based on much larger samples of every Sp/L than any other previously determined infrared colours. The colours obtained are compared with those obtained by other authors. In the present system of infrared colours, the intrinsic (B - V )o values obtained in the programme to determine the intrinsic ultraviolet colours of OB stars (Papaj, Kretowski & Wegner) were used. The majority of slightly reddened Oe and Be stars and all very strongly reddened Be stars adopted in this work are placed on the two-colour diagrams identically as normal B stars. Examples of several two-colour diagrams are presented. Key words: stars: fundamental parameters - dust, extinction - infrared: stars.