@d-healey ah that's fantastic thankyou. I'll try that when I fire up the laptop shortly.

Thankyou for testing and finding the solution, it is much appreciated. I don't think I'd ever have found that!

@ustk
Good Call!

Turning off custom graphics (unintuitively) fixed my main issue.
Now your mentioned problem comes into play not getting my image names correctly, but I should be able to fix that.

Tank you!

@d-healey @Christoph-Hart
ok, than I'll do it that way!
Thanks!

@d-healey Thank you!!

@d-healey Agree! +1

just to thank you guys, I did this code above of my reply and did some editing for 4 samplers and 4 keyboards, I hope it help a newbie like me.

const var Sampler1 = Synth.getChildSynth("Sampler1");

reg i;

for (i = 0; i < 127; i++)
{
if (Sampler1.asSampler().isNoteNumberMapped(i))
Engine.setKeyColour(i, Colours.withAlpha(Colours.blue, 0.2));
}

const var Sampler2 = Synth.getChildSynth("Sampler2");

reg i2;

for (i = 0; i < 127; i++)
{
if (Sampler2.asSampler().isNoteNumberMapped(i))
Engine.setKeyColour(i, Colours.withAlpha(Colours.yellow, 0.3));
}
const var Sampler3 = Synth.getChildSynth("Sampler3");

reg i3;

for (i = 0; i < 127; i++)
{
if (Sampler3.asSampler().isNoteNumberMapped(i))
Engine.setKeyColour(i, Colours.withAlpha(Colours.orange, 0.3));
}

const var Sampler4 = Synth.getChildSynth("Sampler4");

reg i4;

for (i = 0; i < 127; i++)
{
if (Sampler4.asSampler().isNoteNumberMapped(i))
Engine.setKeyColour(i, Colours.withAlpha(Colours.red, 0.3));
}