polymorph:
It makes no difference the color of the case of the LED - only the receiver. You want it to appear black, because that is an IR pass/visible block filter.liudr, are wet erase black markers transparent to IR?
I would just buy an IR phototransistor. If it doesn't have a black casing, it isn't only IR.
Many with clear cases are sold as IR photo-transistors, as in the link in post #10. Just not intended for use in the open.
And none of this explains why his circuit doesn't work in the dark.