Dust tends to be the inverse of the projected colour and shows up on a brighter scene more clearly. IE: dust on the green panel looks like a purple splodge on a white background.
I would say that if it's more visible on darker scenes it's a stuck pixel, but it could be dust on an absorber panel that's allowing light to reflect back to the screen. Try @ChuckMountain s focus check first and see what becomes visible. If the dot is in focus with the image itself it's definitely a stuck pixel.
Hi @ChuckMountain & @noiseboy72 , thank you both for your replies and valuable information. I’ve just tried the focus test. When I take it out of focus either way the green blob disappears completely. As soon as I bring it back to focus it comes back. What would this mean?
Ah okay @noiseboy72. Do you know if this is an expensive repair? I think I might just live with it, I’ve just watched a film and I didn’t seem to notice it. As soon as I turn on ‘AV Mute’ however it’s instantly visible. Thanks again.