Its just a section of line that has a lead core which helps the line sink to a desired depth. I start by putting a few hundred feet of 30lb braid on my reel and then I put a desired section of leadcore on. every 10 yards it changes color so when you here 'colors' its just another way of saying how much lead core line you are using.
If your trolling around 2.5 mph you can approx say every color is 5 feet down. so 5 color will fish around 25 ft down and 7 color is 35 ft. but have to remember depth changes with speed and the size of lure you are pulling. 5 ft/color is the standard for a spoon.
I follow my leadcore with a 40ft flourocarbon leader.
for best results make sure you put the whole section of leadcore into the water.
You can also get it segmented so you have sections of braid in the middle of sections of leadcore. that way you can have a 3+3+4 leadcore reel. so you got a 3,6 or 10 leadcore for different times of the season.
I use leadcore a lot and have 1,2,3,4,5,7,8,10,12 colors on my boat for pike in LPB and walleye. right now 3-7 will work good and in a few weeks you will start getting them more off 8-12 colors.
its hard to get a spoon far away from the boat without using a downrigger(you would need a LONG lead) or dipsey and its a great tool to have in your boat.
Ill be in Burwell on weekends so feel free to talk to me down there.
Hope this helps
www.southcoastcharter.com
southcoastcharter@gmail.com
519.732.4579