can't find the key to finding the 9th color code?

So I have a task there are 8 colors given and i need to find 9th one these are the hex codes for colors

1. #AA0099 ? #009966 = #AA99FF
2. #339900 ? #990066 = #AA9966
3. #006699 ? #EF4321 = #??????

what actions do i have to do to get the last color and why ? this is what it looks like