$10^x$: d. blue (B)
$e^x$: a. green (G)
$\log(x)$: c. red (R)
$\ln(x)$: b. black (K)
\\( \boxed{
\begin{aligned}
10^x &: \text{ d. blue (B)} \\
e^x &: \text{ a. green (G)} \\
\log(x) &: \text{ c. red (R)} \\
\ln(x) &: \text{ b. black (K)}
\end{aligned}
} \\)