Ways to dye liquid

[Da9L]

I would like to get a purple dye for my liquid in one lamp. I thought that mixing blue food dye with red  food dye would do it, but the red color disappears over time for some reason. 

Is there any other way to dye your liquid that is better than using food coloring ?

[Keith]

I like to use ink squeezed from highlighter pens.  I've had good success with blue and decent results with orange.  I haven't tried other colors or mixing colors.

Someone mentioned using printer cartridge refill ink, which makes sense to me.  I've thought about trying that but haven't colored any lamps lately!

[Keith]

http://oozinggoo.ning.com/forum/topics/adding-color-to-globe-fluid

[Verax]

I've used food coloring a lot, and that seems to fade after 3+ months.  (even when not exposed to sun)

Like Keith, I have had good success with highlighter ink.  I've used blue, green, and purple with good success.  After 6+ months, my blue started getting a little cloudy, but I can't say if that was from the ink, the wax (gookit), or some other problem.

[Tim Gill]

 https://www.amazon.co.uk/Purple-Water-Dye-Perfect-Weddings/dp/B004W...

Haven't tried this myself but it looks promising, food dye seams to fade quite quickly I have found.