Usually, I’m very reluctant to use filters: polarization filters are very nice to eliminate or enhance reflections, make for a much more dramatic sky or saturated colours.
I sometimes use a neutral gray filter to reduce contrasts (the filter darkens the bright parts of the picture) and a UV filter may be handy in the mountains or at the seaside.
Colour Filters are something different altogether: even if you can change the colour of the sky to a beautiful blue, the rest of the photo will make clear that something is wrong.

Here’s one example, where I liked the effect of a tobacco filter:

Without Filter:

In this case, I prefer the mood with filter to the unfiltered original. It actually comes closer to what I saw on this rainy day in Blandy’s Garden, Madeira (Portugal)

Some photo tips.

I rented a Braun slide scanner that is able to scan up to 100 slides in one go. This could be the perfect solution for me - I have thousands of unscanned slides.
Unfortunately, although this is a very good idea, the scanner itself still leaves a lot to be desired. Colours are fairly neutral, but very often, it will not correctly detect the format of a picture and try to scan a “portrait” as a “landscape” or vice versa.. It’s also quite fond of simply cutting of parts of dark pictures. A nightmare for night photographers.
Having said that, I was able to scan quite a few pictures, so the future of these pages is not in doubt.

even though the building may be in bad repair, the flowers are quite attractive.