Pretty sure any red or green laser pointer will work. Clear colloidal silver is nano size - tiniest of particles. After a few days if it turns yellow, some silver has clumped together. I think I read somewhere that the yellow tone is the silver particles reflecting the light. So the larger the particles or the most concentrated will have a color tone. But nano size the silver particles are so tiny, it does not have a yellow tone. But the laser can pick it up.
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