ETA: Actually this could use a little explanation. That link is just a random brown that I selected, but your question was about a specific shade of red, so here’s how to find the specific hex code:
Let’s assume your primary red is FF0000, and your primary orange is FFA500
Open the tool, and enter the hex for the shade you’re trying to match: 0F0000. You’ll see that there are other options for colour selection, RGB, CMYK, HSV and HSL. We’re interested in HSV
HSV is Hue, Saturation, Value. The last number, Value is what we’re interested in. 6% in this case.
Now enter the primary color you want to match: FFA500. You’ll notice that the only the first and last number of HSV are different. If you set the last number to what we found earlier, 6% you’ll get an equivalent color and the hex code for it:
Hex?
https://share.google/SGdegy9zSrJEzlMYY
ETA: Actually this could use a little explanation. That link is just a random brown that I selected, but your question was about a specific shade of red, so here’s how to find the specific hex code:
Let’s assume your primary red is FF0000, and your primary orange is FFA500
Open the tool, and enter the hex for the shade you’re trying to match: 0F0000. You’ll see that there are other options for colour selection, RGB, CMYK, HSV and HSL. We’re interested in HSV
HSV is Hue, Saturation, Value. The last number, Value is what we’re interested in. 6% in this case.
Now enter the primary color you want to match: FFA500. You’ll notice that the only the first and last number of HSV are different. If you set the last number to what we found earlier, 6% you’ll get an equivalent color and the hex code for it:
#0F0A00