With white tape under the cable you can use any 1/8" white sleeving - even the worst (like AC-Ryan or Techflex Flexo PET) - to achieve a pure white look from the distance. On closeup view you would see the open weave extremely and it still looks like a plastic cable because of that.

Since you are from Sweden - maybe go to www.reichelt.de - enter "PSK Crimpzange" into the search field - and order this fantastic tool. Supergood and very price-friendly.

At ATX usually AWG18 and AWG20 is used. The smaller the number, the bigger the cable.