I was trying to recreate Predator / Gray Fox stealth camouflage for Mugen.
Using a PalAdd and AfterImage trick this is what I got.
Values will need some fixes based on sprite type (Pixel art / digitized) your character is.
And it do not works on statedef -2, only at -1 or -3.
[State -1, GlassBodyAFT]
type = AfterImage
trigger1 = 1 ;Var() != 0 ; To enable/disable by var
ignorehitpause = 1
time = 2
length = 2 ;set 2 to bind to the char
framegap = 1 ;Set 1 to not delay
palcolor = 1
palinvertall = 0 ;set 1 to invert, sometimes is needed
palcontrast = 25,25,25 ;less is more transparency
palmul = 0,0,0 ;light a bit, set negative to more transparency
trans = sub
[State -1, NoShadow] ;disable shadow and floor reflection
type = assertspecial
trigger1 = 1 ;Var() != 0
ignorehitpause = 1
flag = noshadow
[State -1, Transparency] ;char transparency
type = trans
trigger1 = 1 ;Var() != 0
trans = add
[State -1, GlassBodyP1] ;Char bright parts
type = PalFX
trigger1 = 1 ;Var() != 0
time = 1
invertall = 1 ;invert if needed
add = -220,-220,-220 ;more for subtle effect
sinadd = -5,-5,-5,100 ;disable to not blink
color = 1
(https://i.imgur.com/oYv9Qey.png)