Dear Barbara,
Please pardon the delay in responding to your post. Cadmium Scarlet is very close to both Vermilion and to Cadmium Red
Light. They are all orange-reds, with Cadmium Scarlet being the warmest, then the Vermilion, then the Cadmium Red Light.
In Stephen Quiller's
Color Choices he indicates that Winsor & Newton's Vermilion and Grumbacher's Cadmium Red Light are most similar to the Cadmium Scarlet.
If you are using a Cadmium Red Medium or Deep, you may have difficulty since they are considerably cooler in temperature than any of the Cadmium Scarlet alternatives. However, you could warm either color with Cadmium orange, if you have it.
I wasn't sure if you were interested in a more complete painting critique, or are really concentrating on color mixing in your painting.
Here is my Isabel, 12" x 16".