The stuff only has to look milky; not be milky to achieve your goal.
When I shoot liquids for advertising that I want to glow (or look like they do) such as a glass of frosty beer or a jar of marmalade jam, etc, I put a reflector card behind the subject and let the light show through the liquid.
Using this technique allows me to vary the lighting in a very controlled way that mixing unknown substances don't. If your liquid stuff is too thick or too thin you won't achieve the effect you're striving for. All you have to do is slightly angle the reflectors for each test tube or flask in your set-up.
Product photographers have been doing this for years.
If you choose the colours for the card reflectors, you can get any colours you want sitting right next to each other. Green next to fluorescent red is easy to achieve this way without using coloured liquids at all. For white, use a white card. For blue, use a blue one, etc.
Trim the cards carefully so they don't show.
LED lights are adjustable but you'll find the stray light hard to harness. Different hues of stray light will mix giving you neutrals which will diminish your intended effect. You'll see the problems in the final shot.
If you were shooting functional props for motion pictures, your way would be necessary due to handling by the talent, angles for shots would be uncontrolled, and the lighting problems for that situation are difficult.