Depending on other factors, color catchers may or may not be enough. If you have scraps of the fabrics available, I would recommend cutting a small square of an inch or two of each. Slosh each one in water, then lay on a pad of paper towels. If nothing bleeds into the paper towel, then a few color catchers in your wash will be enough. If anything bleeds significantly, then you need to consider other factors. (1) How much water the washing machine uses can be a factor. Typically, for a first wash when you are nervous about possible bleeding, you want a machine that uses a *lot* of water so any dye bleeds are diluted. If you have a significant dye bleed in a domestic front loader, chances are there will not be enough water to dilute the bleed, making the chances of transfer of color greater. (2) You want to be careful to remove the quilt *immediately* from the washing machine when finished. If you have wet fabric lying against wet fabric for any period of time, the chance of unwanted dye transfer increases. (3) If any of your sample fabrics bleeds a lot, you should use Synthrapol as your detergent. Synthrapol suspends loose dye particles in the wash water so the dye does not settle into other fabrics. It is more effective than color catchers, although you can use both in the same wash water if you like.
Most dyes these days are pretty stable, plus not all fabrics accept loose dye particles. How safe you want to be on the first wash of your quilt is really a matter of personal preference. Color catchers are often enough. However, if you are unlucky enough to have a strong bleeder fabric, they may not catch everything. That's why I like to use Synthrapol. Testing all of the fabrics that concern you will give you a pretty good indication of whether color catchers will be enough or not.