K $\leq~T_{\rm eff}~\leq~4750$ K (K7V - K3V)

($b-v$) $\in~[1.00;1.30]$\
$B-b = -0.074 - 0.010 (b-v) \pm 10^{-3}$

$4750$ K $\leq~T_{\rm eff}~\leq~10500$ K (K3V - B9V)

($b-v$) $\in~[-0.05;1.00]$\
$B-b = -0.085 (b-v) \pm 10^{-3}$

$10500$ K $\leq~T_{\rm eff}~\leq~35000$ K (B9V - O8V)

($b-v$) $\in~[-0.30;-0.05]$\
$B-b =  -0.073 (b-v) -0.065 (b-v)^2 \pm 10^{-3}$

A third order fit can be applied to the whole interval:

$4750$ K $\leq~T_{\rm eff}~\leq~35000$ K (K3V - O8V)

($b-v$) $\in~[-0.30;1.00]$\
$B-b = -0.070 (b-v) - 0.040 (b-v)^2 + 0.026 (b-v)^3 \pm 10^{-3}$

### ($B-b$) vs ($u-b$)

$4250$ K $\leq~T_{\rm eff}~\leq~5500$ K (K6V - G8V)

($u-b$) $\in~[0.20;1.30]$\
$B-b =  -0.056 - 0.060  (u-b) + 0.028 (u-b)^2 \pm 10^{-3}$

$5500$ K $\leq~T_{\rm eff}~\leq~10500$ K (G8V - B9V)

($u-b$) $\in~[-0.15;0.20]$\
No possible transformation.

$10500$ K $\leq~T_{\rm eff}~\leq~35000$ K (B9V - O8V)

($u-b$) $\in~[-1.40;-0.15]$\
$B-b =  0.003 - 0.009  (u-b) \pm 10^{-3}$

### ($V-v$) vs ($b-v$)

$4000$ K $\leq~T_{\rm eff}~\leq~5250$ K (K7V - K0V)

($b-v$) $\in~[0.85;1.30]$\
$V-v =  0.061 - 0.136 (b-v) \pm 10^{-3}$

$5250$ K $\leq~T_{\rm eff}~\leq~8750$ K (K0V - A3V)

($b-v$) $\in~[0.07;0.85]$\
$V-v =  0.0025 - 0.068 (b-v) \pm 10^{-3}$

$8750$ K $\leq~T_{\rm eff}~\leq~30000$ K (A3V - B0V)

($b-v$) $\in~[-0.30;0.07]$\
$V-v =  -0.001 - 0.033 (b-v) \pm 10^{-3}$

A second 