From the flowers I’ve seen in online photos of Hoya sp. aff. kenejiana (Red Corona) there are considerable differences in the color.  There are many that look like mine, and others that are much lighter yellow with a brighter red in the corona.  I think that it is variable dependent upon the conditions under which the plant is grown.

The plant did very well for me growing outdoors in the greenhouse over the summer putting on many new leaves and actually flowered for the second time just before bringing it back inside. You can barely detect the red in the corona in this flowering.