This pattern is considered a pinto pattern by a lot of people, or perhaps piebald or skewbald but it's a bit more complicated than that. Splash in it's most minimal form can be seen as just normal markings, or sometimes no markings at all even. But in extreme cases you get a horse that has even more white then colour. This is something a lot of breeders do not want because these ponies will often get registerd section X instead of their true section. They are pureblood Welsh Ponies but because they look piebald/skewbald they aren't accepted while their parents carry the exact same white gene only less visible. In my opinion this is wrong. I do not consider Splash to be a pinto pattern but just a gene that can cause very loud (beautiful) markings.
Splash is actually very common among Welsh Ponies. Signs that give away the presence of Splash:
Blue eyes
When a Welsh Pony has (partially) blue eyes (without being a double diluted cream) it is definitely a Splash carrier, even if it doesn't have any white markings. Only Splash and Frame Overo give blue eyes but Frame does not exists withing the Welsh breed so you can be sure this pony has the Splash gene.
Bottom heavy blaze
Another frequently seen sign. A blaze that gets wider at the bottom, often covering the nostrils completely or partially. And often together with (4) white socks with straight edges. These markings have been very wanted by a lot breeders, but breeding them together there is a change of getting a very loud Splash foal. Even the loud splashed white horses will often have a bald face that is heavier at the bottom.
Belly spot
Now this one is a bit tricky because there are two genes that can cause this, Splash and Sabino, but even more often these genes are seen together making this even more difficult. But a belly spot often comes together with the sign discribed above. The belly spot can be as tiny as a few hairs, but it can also be so wide spread it covers most of the body, often connecting with the white markings of the legs making the pony look piebald/skewbald.