What happens when a coloured oxide reacts with a hot concentrated alkali

Dear student,

The coloured oxide is lead monoxide (PbO) when it reacts with a hot concentrated alkali then Na₂PbO₂ (Lead (II) sodium oxide) is formed. The Colour of Na₂PbO₂ is light yellow which is also the colour of lead monoxide, hence the colour remains as such.
The reaction is as follows- 
 

PbO + 2NaOH → Na₂PbO₂ + H₂O

Regards