[Nexodusrex]

I remember this toyline, it was a series of figures and vehicles. the figures were smallish, like M.A.S.K. size.
the gimmick was they used water to make themselves invisible through color change. there was a small set with 2 vats that you dip figures in to turn them invisible.
for the life of me I cant remember what they are called, but I do know they exist.

[Bradsdadg]

I believe they are called Shadow Strikers. They were made by Kenner along with the MASK figures. I do not know anything about them, except I happened to watch Pixel Dan's 2012 Dec youtube video where he tours his collection and he mentioned them, and I saw this post of yours. Hope this helps!