Measurements up to 9x5.5 mm, with 4.5 whorls. General shape moderately high, similar to that of T. pullus pullus but the upper part of the whorls is somewhat flatter, less inflated. Surface of shell is smooth and glossy, with indistinct growth lines. A very line spiral microsculpture may be seen under favourable conditions, especially on very juvenile shells. The shell material is somewhat translucent even in very adult shells. Aperture is oval-rounded, inner lip closely appressed without any umbilicus or chink in the adult. Colour pattern. Colour pattern includes red and/or brown (rarely orange) markings on a translucent, whitish to brownish background. It may also include smalt opaque-white patches. Most commonly, there are large red or brown flames under the suture and wavy oblique lines running from there downwards. A very constant design is found on the base of the shell, and consists of a series of regular oblique lines starting from the columella upwards, and merging shortly into a series of spiral blotches. There are individuals with rarer colour patterns (e.g. entirely white, or dark brown, or completely covered by fine, very regular oblique lines).

Tricolia pullus picta appears as the representative of the group on the continental Atlantic coast, from the British Isles to Morocco.
T. pullus picta differs from T. pullus pullus by
(1) thinner shell, of more translucent material,
(2) whorls more flattened in their upper part,
(3) polychromatism with a dominance of the zigzag oblique lines and
(4) the characteristic oblique lines at the base of the last whorl.
As it has been stated with general remarks on the T. pullus group, there are localities in the Straits of Gibraltar area where 7 T. pullus pullus, T. pullus picta, T. tenuis and transitional morphologies may occur sympatrically without these taxa being separable. Such localities include M'diq in northern Morocco, Cadiz, Barbate, Getares, Calahonda, Marbella in southern Spain. Extreme variants selected from a population in this area may be entirely similar to Atlantic T. pullus picta or to Mediterranean T. tenuis, while T. pullus pullus morphs are not very typical (smaller size, polychromatism with T. pullus picta trends).
Transitional individuals between T. pullus picta and typical T. pullus pullus are otherwise found on the Algerian coast and in southernmost Italy and Sicily.

This subspecies ranges from the British Isles, inclusively, south to at least Tarfaya, Morocco (Bellon-Humbert, 1976). There are no other data available for the Saharan coast, and typical expression of this subspecies has not been found on the African coast further south. In our opinion, all reports of T. pullus s.l. from British Isles, western France and northern Spain should be referred to T. pullus picta. In the western Mediterranean, transitional morphologies and colour patterns approaching T. pullus pullus and T. tenuis are found locally (sec under remarks).
F. pullus picta is found on seaweed in the infralittoral, from low water of spring tides, in moderately sheltered to quite exposed localities. It seems to favour gelatinous red algae (e.g. Chondrus crispus).