Feria highlights

I saw this in Sav-on and I have colored medium brown with red undertones. This is natural and the color is to cover grey, I'd like to do some 'redder' highlights and was wondering if the Feria red (Mahogany?) would work on pre colored hair or is it for virgin hair only?

Is it used wet or dry, the boxes in Sav-On were sealed I couldn't read the directions and no mention is made on the box.

Anyone here use it and have recommendations yea or nay?

TIA,

Okay, I have Feria Colour Strands QuickShimmer Highlights in Red Currents. Is this what you mean? I have not been brave enough to do it yet, I've probably had this going on months now. What can I look up for you, dear? I can open the box, so what exactly should I look for? First question to answer. It says make sure your hair is dry and unshampooed. It doesn't say anything about you having to have virgin hair and I know you are meaning uncolored hair. Anything else I can help you with?

I suggest you go with a red that's less drastic, that way if it doesn't come out the way you want it, it won't be so 'noticeable'.