Choosing a type of grout is much more complex than just finding a color, and can be a daunting task if you don't understand exactly what kind of grout you should use for your project. It is very important to understand the specifications of grout so that you can make a properly informed decision and make your project as successful as possible. There are two major classifications of grout: Portland cement grout and epoxy grout. Within these two major categories, there are two basic types known as sanded and non-sanded. When dealing with joints 1/8 inch or larger, sanded should be used, and when joints are less than 1/8 inch, non-sanded.
When discussing epoxy grout, these have special attributes necessary and the applications tend to involve chemical or thermal resistance. 100% epoxy resin grout is made of 100% epoxy, consisting of epoxy resin, silica fillers, pigments and a hardener. They are resistant to staining, have a very low water absorption rate, are resistant to chemicals and have a higher compressive strength than concrete. They may cost more but it will save you time and energy in the long run with maintenance.
Non-sanded Portland cement dry-set grout consists of cement, fine fillers, water-retentive additive and pigment and is designed for tile surfaces that are dry when the grout is applied. It is typically used for easily scratched tiles and wall joints from 1/32″ to 1/8″. For moistened tiles, sanded Portland cement grout will work well, consisting of fine graded sand, cement, pigment and sometimes water retentive additives, though it does need to be damp cured. Latex-modified sanded Portland cement grout is very similar to the sanded Portland cement, except that a latex polymer is involved, which increases its water resistance and bonding characteristics. These grouts do require sealant afterwards to protect against damage and staining and a bit more maintenance than epoxy, but cost less.