color variation with toluidine blue?

Hi all, I have a question I have not been able to resolve through an
exhaustive search and thought I would give it a try here.

I am working with histological sections for entomology, heating them and
applying Toluidine Blue .5%, and my sections come out nicely stained, but
all blue. Meanwhile, I have older slides from someone else to look at which
exhibit a fairly wide and striking color range, from green through blue to
violet-pink, apparently also stained with T Blue.

Apparently this is known as 'metachromasy' (?) and has something to do
with pH of the stain or fixation, but I cannot find any particulars. Anyone
know how I can achieve this effect, or a source I can consult?

Thanks in advance! =)


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