It is very unstable and will explode with impact, static friction, or heat!!
However, additional purification is possible, adding both greater stability and more robust (explosive) reaction. This purified mercury fuliminate is pure white.
The materials needed are high concentration ammonium hydroxide solution (NH4OH) and glacial acetic acid (C2H4O2). All of this stuff is extremely dangerous to handle and breathe.
If you were thinking about nitroglycerin... it is fluid, oily... but yellow...
My answer was given for accuracy purposes only. Don't play with fire, don't hurt living things- including people!