a general relation for the whole set of temperatures:

$4000$ K $\leq~T_{\rm eff}~\leq~35000$ K (K7V - O8V)

($uvw1-v$) $\in~[-2.45;4.50]$\
$U-V =  0.023 + 0.596 (uvw1-v) \pm 4.10^{-2}$

Giants
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Whenever a colour transformation is possible for MS stars, it is generally also satisfactorily obeyed by giant stars. The difference essentially lies in the validity range of the colour transformations. Each time a forbidden zone appears in the temperature domain (i.e. each time there is a zero in Table 2), the transformation relative to the hottest stars remains valid for giant stars down to $\sim 250$ K cooler than the lower temperature bound defined for MS stars. Symmetrically, the transformation relative to the coolest giant stars is only valid from stars $\sim  250$ K cooler than the upper bound of the temperature interval defined for the corresponding MS star colour transformation (see Fig. 3a).

When colour transformations are possible for MS stars on the whole temperature domain, they are generally valid for giant stars as well (Fig. 2).

Metal poor stars
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In this case, the situation is worse. Stars still obey the same relations as MS stars when colour transformations exist on the whole temperature domain. Even in other cases, 