Define colours of markers of scatterplot by rgb-values

Question

I want to colour the markers of a scatter3 plot in specified colours with rgb values. I tried it before in the following way:

\documentclass[]{article}
\usepackage{pgfplots}

\begin{document}
\begin{figure}[H]
\centering
\begin{tikzpicture}
\centering
    \begin{axis}[
view={100}{35},
width=255pt,
height=255pt,
z buffer=sort,
xlabel={$R$},
ylabel={$G$},
zlabel={$B$},
point meta=explicit,colormap/bluered,
scatter/use mapped color={ball color=mapped color},
]
\addplot3[only marks,scatter,mark size=2.5,
scatter/classes= {0={mark=ball, }}]
table[x=R,y=G,z=B,meta=C] {Scatterplot.txt};
\end{axis}
\end{tikzpicture}
\caption{Caption}
\label{label}
 \end{figure}
 \end{document}

In this try the data in Scatterplot.txt was divide in the following way:

R G B C
0.68235 0.67843 0.44314 1
0.68235 0.67451 0.45098 1
0.68235 0.67059 0.4549 2
0.67843 0.66667 0.4549 5
0.68235 0.67451 0.45882 4
0.68235 0.68235 0.46275 3
0.6902 0.69412 0.47451 2

It plotted the scatter plot like I wanted. The dots were in the colour cube and had 5 different colours. Those colours were just the ones defined by a predefined colourmap.

The problem is now, that i want to have the marker in a colour specified by three columns in Scatterplot.txt.

The file Scatterplot.txt now looks like:

R G B RED GREEN BLUE
0.68235 0.67843 0.44314 0.7653 0.74446 0.33547
0.68235 0.67451 0.45098 0.7653 0.74446 0.33547
0.68235 0.67059 0.4549 0.7653 0.74446 0.33547
0.67843 0.66667 0.4549 0.7653 0.74446 0.33547
0.68235 0.67451 0.45882 0.7653 0.74446 0.33547
0.68235 0.68235 0.46275 0.7653 0.74446 0.33547
0.6902 0.69412 0.47451 0.7653 0.74446 0.33547

So instead of 4 columns with 3 coordinates and a single "colourvalue" I want to have the markers still at the coordinates of the first 3 columns, but coloured in the rgb value defined in the last 3 columns.

This is the first question I asked here and i hope that it is in the format how you normally do this here. If not please let me know so I can do it better next time.

Note, that i found the question

How to plot scatter points using pgfplots with color defined from table rgb values

which is similar to mine, but I was not able to make it work with a

addplot3

command.