At 5 weeks old, your litter's points (ears, face, legs, paws, tail) are really only starting to deepen, so it may be as many as 3 to 5 more weeks before you can make a more educated assessment of their point color. You should have more certainty by the time they are 12 weeks old. Some good indicators would be eye color, point color, body color, nose leather and paw pad color.
In a seal point, the eyes will be a clear, brilliant, deep blue, the points will be a seal brown (very dark) and the body will be a cream shading gradually into pale warm fawn on the back. Seal point kittens will usually be pale in color. The nose leather and paw pads are normally seal brown.
In a blue point, the eyes are clear, vivid blue. The points are light blue (grey). The body is glacial white, shading gradually into blue on the back, same as the points but a lighter color. The nose leather and paw pads are blue.
A chocolate point will have clear, bright, vivid blue eyes, the points will be a milk chocolate color, the legs will be paler and the body is ivory all over with little or no shading into the points. The nose leather and paw pads are a chocolate or pinkish chocolate color.
Lilac points will have clear, vivid blue eyes, the points are pinkish grey, the body is off-white (I think of a magnolia *smile*) with little or no shading into the points. The nose leather and paw pads are pinkish/faded lilac.
While I feel certain that you will want to do the best job possible for your babies, I also feel compelled to remind you that *Siamese kittens are not ready to leave their mothers before 12 weeks of age*. They seem to need those extra few weeks to develop fully and properly more so than other kittens do, so in order to ensure a happier placement for them when the time comes, remember that, OK?
Hope this helps you, and if I can be of further assistance to you, please don't hesitate to contact me. I am still somewhat new to the wonderful world of breeding Traditional Siamese myself, but I can put you in touch with some really wonderful, very knowledgable people who are ethical, responsible breeders of pedigreed Siamese cats.
Best of luck to you,