Аннотация:It is shown that the dependence of colour indices B-V and U-B on the V-brightness has a heterogeneous character. The V-brightness decreases from its maximum (9m.4) to some intermediate value (10m.6) is accompanied by the increase of colour indices with their following decrease when the brightness drops up to V ≈ 11m.7. Such a dependence, found earlier for several irregular variable stars, indicates to a relation of these two types of variables.