correct, the RSMGIDRatioColor is (tentatively) expected to behave as index / total_number.
You can check the index in the Transform -> Display attribute of the cloner object (check the screenshot below).

Cheers,
Ilia

(index/total number) or (1 - index/total number)

Cheers

So, the code I showed you has an expiration date.

Thank you for your question. I just checked, and what RS calls the index ratio does not really have much to do with indices and is instead based on the uvw coordinate of a particle. This might be a bug, but you would have to talk with the Redshift team for that. Anyway, find below some Python code to emulate computing that 'index ratio'.

Cheers,
Ferdinand

Result

I emulated your setup:

Code

import c4d
import mxutils

doc: c4d.documents.BaseDocument  # The currently active document.
op: c4d.BaseObject | None  # The primary selected object in `doc`. Can be `None`.


def main() -> None:
    """Called by Cinema 4D when the script is being executed.
    """
    data: c4d.modules.mograph.MoData = mxutils.CheckType(c4d.modules.mograph.GeGetMoData(op))
    uvw: list[c4d.Matrix] = data.GetArray(c4d.MODATA_UVW)
    for i in range(data.GetCount()):
        # That is how the 'index ratio' is computed, it is effectively just the shifted x-component
        # of the uvw coordinate of the particle. The color is then just (ratio, ratio, ratio). Not very
        # 'indexy'.
        ratio: float = 1 - uvw[i].x
        print(f"{i}: {ratio}")

if __name__ == '__main__':
    main()