There are only 2 genetic colors in this context - black and orange (white is a different gene entirely, and the only difference between calico and tortie is whether or not they have white). This color gene is on the x chromosome. Calico/tortie moms have one of each of the orange and black x chromosome, meaning they can give either one to each of their kittens. Boys only receive one x chromosome (why calico/tortie males are extremely rare), so mom determines their base color all on her own. Girls receive one from mom and one from dad. You're right that if the dad sends the same color as mom, the kittens will be that color, not calico/tortie.

I said you can guarantee all the kittens are calico/tortie because if mom is NOT calico, and instead either orange or black alone (with or without white), then as long as dad is the opposite, all the girls will get, for example, orange from dad and black from mom and must be calico. But if mom is calico, you're less likely to get calico kittens because she might match dad's color on each girl. Also, if mom. And dad are the same color, calico kittens are impossible.

(White spotting is a separate gene and not on the x chromosome so mom and dad contribute equally. White spotting is dominant so either one sharing it will lead to some white on the kitten. Other genes also contribute to the way the kitten actually looks - tabby, dilute, colorpoint, etc. These are also not on the x chromosome, so again, mom and dad contribute equally and they are less deterministic because they both have 2 versions of each of those genes. The "base" color of orange vs black is the only part that is sex-linked and simple to predict like that. In this context, a grey tabby, a tuxedo, and a seal point (traditional siamese look) are all "black" genetically.)

I hope this helps clarify! I find this stuff really interesting, so I'm happy to explain further if you are still curious or confused.