i like that one grainy mustard thats slightly brown but idk what they do to it
its really good texture and flavour
You're thinking of dijon, and it's what they
don't do to it that makes it grainy and brown. The general idea behind any mustard is you take mustard seeds and soak them in some sort of acid (usually vinegar, but can also be certain wines) until they become soft. Then you smash them up until they become mustard.
Normal yellow mustard usually uses the really light seeds which are the least spicy and don't have that dark sorta color, then they grind them up with a food processor, press the mixture through a fine screen to filter out the husks from the seeds (which are the 'grainy' stuff) and then reprocess again until really fine paste, which usually gets a lot of sugar and extra stuff added to mask the spiciness of the mustard and get the normal, vinegar taste.
Dijon mustards use a darker seed that's spicier, without being ground and filtered as much as the normal hotdog mustard. The rule of thumb is basically, the darker the seed, the spicier the mustard.
Source: have made homemade mustard