Hand pour question

I have a RTV mold I made for a float n fly application. It's. 3" minnow type cavity hand made . I was thinking on the lines of a core shot, for a lateral line look. What do you guys think if I take a pair of scissors and make a small strip, maybe smaller than a tooth pick of a already mixed dark color, make my first pour, let it set just enough to lay the small sliver of plastic in the middle then finish the cavity. Think it will run the dark color into the main body color?

your gone through a lot of trouble to make a bloodline you could do the following shoot half of your mold most likely if you got a laminate plate would be handy take That mold and take a toothpick and put a dab of coloring on the upper head and of your plastic put your mold back together and shoot it.