Thanks for your replies!
@Bill Kielb yes, Fiesta ware is the exact look I'm after - and yes, totally aware that an appropriate glaze is needed so would be looking for a semi-matte (or matte if you can use that for tableware) clear to go over top and really make the colours POP. Thanks for the recommendations @neilestrick
@Min I've definitely considered the cost of colouring my clay body (even though that's really the look I'd love - bright coloured body with clear glaze over top). By flat I really mean solid pigmentation (so I guess I can paint the underglaze all over) but I'd also like to achieve as matte a finish as tableware (foodsafe) will allow also.
Can any underglazer remain exposed/unglazed or will it wear and be unsafe for food?