$\mathrm{CrO}_4^{2-}$ (yellow) changes to $\mathrm{Cr}_2\mathrm{O}_3^{2-}$ (orange) in $\mathrm{pH} = \mathrm{x}$ and vice-versa in $\mathrm{pH} = y \cdot \mathrm{x}$ and $\mathrm{y}$ are

This is the chromate-dichromate equilibrium, where the orange ion is intended to be dichromate. In acidic medium, yellow chromate converts to orange dichromate, and in alkaline medium the reverse occurs. The transition is commonly taken around $\mathrm{pH} = 6$ for chromate to dichromate, and the reverse around $\mathrm{pH} = 8$. Thus $x=6$ and $y=\dfrac{8}{6}$. Matching with the given options, this corresponds to the pair $6, 8$.