Do Faraday's gold colloidal solutions still exist?
Please note that I haven't seen the sample myself!

However, the Royal Institution claims that a bottle with the collidal gold solution is on display at Michael Faraday's Magnetic Laboratory (see bottle at the bottom of the image) in the museum of the Royal Institution.

Update

This might be nitpicking and English isn't my native language, but David Thompson does not explicitly state in his article in Gold Bulletin that all samples are lost.

On the other hand, Ryan D. Tweney in his article Discovering Discovery: How Faraday Found the First Metallic Colloid, published in Perspectives on Science, 2006, 14, 97-121 (DOI) not only describes the finding of 700 surviving microscopic slides in Faraday's reconstructed magnetic with gold film samples and numbered in Faraday's hand and that the numbers correspond to the numbering in Faraday's 1856 Diary (lab journal) but continues:


  It had long been known that some of Faraday's gold colloids survive from the 1856 research: Four bottles of these are on display at the Royal Institution in London [&hellip;]. These few colloids are all that survive of many dozens referred to in the Diary.