dometic thermostat upgrade

So I got a Honeywell thermostat but the wiring has me stumped.

There are two fatter wires that control the furnace. These are red and light blue. Put them together and the furnace comes on.

The remaining wires are green, white, blue and red

The thermostat has b, o, g, y, r, rc. The last two have a jumper.

I have searched everywhere with no luck. All the information I found on the net has a yellow and I don't.

Please help