My grafted plant of 'Gorgeous' from Rinoa flowered this morning:
here is it by flash
here is the small graft
here are Mr Ko's and Rinoa's potos of this cultivar
and now for the actual colour. The background colour nearest matches the Royal Horticultural Society's Colour Chart as Yellow Group 2D - not a very deep yellow at all, almost a cream.
Here is a collage of the chart: