For orange there is also regla, sessei, libanensis, betulifolia, pubescens (all section Erythrostachys), x jamensis Pat Vlasto and Devanteville, greggii Lowry's Peach, lasiantha.
As Robin said, it is hard to tell with scarlet forms if they are closer to red than orange.
The standard for determining colors for patents is the RHS Colour Chart. Less expensive and infrequently used is the Pantone Color Formula Guide, used for printing, painting and other graphic standards. I use the Color Picker on Photoshop to read the RGB colors from images (other bitmap graphics have their own versions)