Colour–magnitude diagram of 47 Tuc. Triangles are the stars analysed in this paper: green symbols are our faint stars group, while the magenta ones are the bright stars group. Dots are stars not observed in this paper. For comparison, location of ZAHB stars of different masses and He abundances (Y = 0.25: red dots and solid line; Y = 0.28: blue dots and solid line), the evolutionary tracks off the ZAHB for stars of 0.65   M_⊙ (dashed lines) are also plotted.