If $10 \text{ mL}$ of $H_2SO_4$ is mixed with $10 \text{ mL}$ of $Mg(OH)_2$ of the same concentration, the resultant solution will give the following colour with universal indicator:

When $10 \text{ mL}$ of sulfuric acid ($H_2SO_4$) is mixed with $10 \text{ mL}$ of magnesium hydroxide ($Mg(OH)_2$) of the same concentration, they undergo a complete neutralisation reaction.

$H_2SO_4$ is a diprotic acid that releases two moles of $H^+$ ions per mole of acid, and $Mg(OH)_2$ is a dibasic base that releases two moles of $OH^-$ ions per mole of base. Since both the volume ($10 \text{ mL}$) and the molar concentration are identical, the moles of $H^+$ ions produced by the acid exactly equal the moles of $OH^-$ ions produced by the base:

$$H_2SO_4(aq) + Mg(OH)_2(aq) \rightarrow MgSO_4(aq) + 2H_2O(l)$$

This results in a completely neutral solution with a $pH$ of $7$. According to the pH scale and universal indicator color chart, a neutral solution ($pH = 7$) turns green.

• Why other options are incorrect:
• A (Red): Red indicates a highly acidic solution ($pH$ around $1$ to $3$).
• B (Yellow): Yellow indicates a weakly acidic solution ($pH$ around $5$ to $6$).
• D (Blue): Blue indicates an alkaline solution ($pH$ around $9$ to $10$).