\begin{table}%t4 \caption {\label{tab4}Parameters of fitting equations for color$-$type relationships.} %\centerline {\begin{tabular}{crrrccc} \hline\hline Color & {\it a} & {\it b} & {\it c} & type & $R$ & Sensitivity \\ & & & & Range & & Index$^{{a}}$ \\ \hline $r-i$ & 2.77242 & 0.01930 & $-$0.00355 & [10, 27.5] & 0.62 & 0.073 \\ $i-z$ & 0.89637 & 0.00812 & 0.00582 & [13, 25] & 0.89 & 0.225 \\ $i-J$ & 4.46097 & $-$0.12872 & 0.01099 & [10, 25] & 0.94 & 0.253 \\ $i-H$ & 2.68743 & 0.22692 & 0 & [10, 25] & 0.92 & 0.227 \\ $i-K$ & 2.04847 & 0.39856 & $-$0.00567 & [10, 25] & 0.90 & 0.200 \\ $z-J$ & 1.32530 & 0.10725 & 0 & [10, 13.5] & 0.59 & 0.107 \\ $z-J$ & 0.61620 & 0.10826 & 0 & [19, 26] & 0.81 & 0.107 \\ $z-H$ & 4.23705 & $-$0.31004 & 0.02038 & [10, 14] & 0.70 & 0.158 \\ $z-H$ & 4.60067 & $-$0.03962 & 0 & [17.5, 27.5] & 0.53 & 0.040 \\ $z-K$ & 3.93079 & $-$0.21325 & 0.01860 & [10, 14] & 0.72 & 0.235 \\ $z-K$ & 6.96601 & $-$0.13083 & 0 & [17.5, 27.5] & 0.72 & 0.080 \\ $H-K$ & 0.15050 & 0.03638 & 0 & [10, 15] & 0.40 & 0.040 \\ $H-K$ & 2.19557 & $-$0.08809 & 0 & [17, 25] & 0.66 & 0.088 \\ $J-H$ & 0.06224 & 0.06903 & 0 & [10,14] & 0.49 & 0.088 \\ $J-H$ & 5.58544 & $-$0.21707 & 0 & [20, 25] & 0.90 & 0.100 \\ \hline \end{tabular}} \par \smallskip Notes: the united polynomial fitting equation of color$-$spectral type relationships is: ${\rm color}=a+b({\rm type})+c({\rm type})^{2}$, type~$=$~10 for L0, 15 for L5, 20 for T0, 25 for T5; $^{{a}}$ Sensitivity indices are the rates of change of color ranges with spectral ranges covered by fitting lines. \end{table}