It definitely depends on which genes we're dealing with.
Heterozygous tobiano has a 50% chance of passing down the pinto, and the amount that it is expressed (minimal-maximum) is just up to genetic variation, it is genotypically the same. If you breed two tobianos together, you have a 75% chance of getting a tobiano, 25% chance of solid. Homozygous tobianos will always produce tobiano babies.
Frame overo always has a 50% chance of creating a frame offspring (because all frames are heterozygous), and of course you don't breed two frames together.
Splash overo in homozygous form will always pass down the splash gene. In Heterozygous form it is usually facial white, often blue eyes. When bred to another splash carrier then they can produce a homozygous... i.e loudly expressed.... splash.
And then the more of these patterns you mix together, the greater the chance of having a colorful baby.
Example, my stallion carries tobiano, sabino, splash, and frame, and on top of that is an appaloosa.
The pintos came from his fathers side, the appy from his mother, so he isn't homozygous for anything. So in all likelyhood, he COULD produce a solid it's just highly unlikely. Especially given that the mares I'm breeding him to are a tobiano, tobiano/splash, and a minimal appy. I have an ongoing bet with my friends - if next years foal crop I get a plane brown solid baby, I am going to eat my shirt.