Stannous chloride reduces the gold to colloidal metal giving the violet color.
There can be a couple of reasons you do not get this violet color reaction:
No gold in solution.
Stannous chloride is too old, or not working, (a standard gold solution to test your stannous against can help you determine the problem here).
If you have to much oxidizer in your gold chloride solution (like nitric acid or bleach forming chlorine gas), this will re-dissolve (oxidize) the gold in your reaction, that the stannous chloride is trying to reduce to metal, so you may not see the reaction occur (or you may see it start to turn purple, and disappear), or other metals can some time’s over color the reaction so it may be harder to determine the violet color.
If your stannous is fresh, and will not work, and it is positive for gold, you probably need to gas off the chlorine in your gold solution (to much bleach still left in solution forming chlorine gas) heat works to remove this gas, also make up a known solution of gold and test your stannous with it.
I think before driving that truck you should clean that thick mud off the windshield, so you can see the road, and not run off the side of the mountain, practice learning the stannous chloride test before taking the truck for a spin, it is like working with a clean windshield, you will be able to see where your going.
