aqueous sulphur dioxide

Acidified potassium permanganate solution:
The deep purple solution of potassium permanganate changes to colourless.
This is because the deep purple permanganate ion is reduced to colourless solution, while the colourless sulphur dioxide is oxidized to colourless sulphate ion.
(2MnO4-(aq) + 5SO2(g) + 2H2O(l) → 2Mn2+(aq) + 5SO42-(aq) + 4H+(aq))

Acidified potassium dichromate solution
The orange solution of acidified potassium dichromate changes to green.
This is because the orange dichromate ion is reduced to green chromium(III) ion, while the colourless sulphur dioxide is oxidized to colourless sulphate ion.
(Cr2O72-(aq) + 2H+(aq) + 3SO2(g) → 2Cr3+(aq) + H2O(l) + 3SO42-(aq))

Bromine water
The brown solution of bromine changes to colourless.
This is because the brown bromine solution is reduced to colourless bromide ion, while the colourless sulphur dioxide is oxidized to colourless sulphate ion.
(Br2(aq) + SO2(aq) + 2H2O(l) → 2Br-(aq) + SO42-(aq) + 4H+(aq))

Iron(III) sulphate solution
The brownish yellow solution of iron(III) sulphate changes to pale green.
The brownish yellow iron(III) ion is reduced to pale green iron(II) ion, while the colourless sulphur dioxide is oxidized to colourless sulphate ion.
(2Fe3+(aq) + SO2(g) + 2H2O(l) → 2Fe2+(aq) + SO42-(aq) + 4H+(aq))

Dilute black ink solution
The black ink solution changes to colourless.
This is because the dye in the black ink is reduced to a colourless compound [dye-O], while the colourless sulphur dioxide is oxidized to colourless sulphate ion.
(dye + SO2 + H2O → SO42- + 2H+ + [dye-O])

Wet pH paper
The pH paper changes to red.
This is because sulphur dioxide solution is acidic when dissolves in water. The acidic solution changes to wet pH paper to red.
(Although sulphur dioxide is a bleach agent, it cannot bleach the dyes (indicators) in the pH paper.)
(dye + SO2 + H2O → SO42- + 2H+ + [dye-O])