The simple fact that there's been human activity around the bird table site, together with the 'newness' of the table which has been installed (which might relate to the levels of 'shine' on the two tables, or even to its odour) might explain why birds are currently shunning the new table.
Colour vision in birds is a complex subject, with some species having colour vision biased towards violet (and therefore not too dissimilar to our own) but with other species having colour vision biased towards ultraviolet. (The amount of ultraviolet light being reflected by the new table might be very different to that from the old table. You wouldn't be able to see any difference but it could be obvious to a bird ).
A little light reading for you:
https://academic.oup.com/mbe/article/20/6/855/982805/Complex-Distribution-of-Avian-Color-Vision-Systems