If trying to match sun light (coming in from window) I just put the Blue Gel (CTB) on the light (Halogen pepper light). This will basicly match lighting right?

Nominally you want a full CTB to do that. There isn't just one shade and they all bring a tungsten light to a higher color temperature of one or the other value. I think you'll find though, your going to lose a lot of light going that way and a 150w tungsten will be very watered down afterwards.

it's a 600 watt pepper and I also have a 300 as well.

As mentioned elsewhere repeatedly, transmission factor on a Full CTB is around 25% and around 50% on a half CTB

Full CTB will get close to the daylight coming in. If it's later in the afternoon or earlier in the morning and warmer than 5500K, you might could use 1/2CTB if you need more light, since, as mentioned above, full CTB cuts your light output quite a bit. When using full CTB I generally use 1K lights. In most cases I've got by with 1/2 CTB and let the background daylight go just a bit blue.