homogeneous coordinates of projective scheme

Question

Suppose $R$ is a ring, $P^n_R$ - projective scheme. If $k$ is a field, there is a one to one correspondence between $k$-rational points of $P_k^n$ and $P^n$, given by homogeneous coordinates $[X_0:...:X_n]$. How do homogeneous coordinates work in case of $ProjR[X_0,...,X_n]$, when $R$ is not a field? Is there a good reference about this? I can't seem to find anything explicitly stated anywhere.