Blue HB stars in NGC 288 as observed by Grundahl et al. (1999). The subsample, for which GIRAFFE spectra were observed, is marked by filled circles. The dot-dashed line in the left part marks the u − y colour of the u-jump. Stars on the red side of the line do not show evidence for radiative levitation, while stars on the blue side do. The triangles mark overluminous stars around the u-jump (from red to blue: 122, 103, 127, 101, 146, 142, 100, 183).