To determine which aqueous solution will be colorless, we need to consider the electronic configurations and oxidation states of the ions in each option.

Electronic configurations of the given ions:
- Sc3+: [Ar]3d04s0
- Fe2+: [Ar]3d64s0
- Ti3+: [Ar]3d14s0
- Mn2+: [Ar]3d54s0

The color of a solution is typically due to the presence of transition metal ions, which have partially filled d orbitals. The absorption of certain wavelengths of light by these ions leads to the observed color. In general, ions with unpaired electrons in their d orbitals tend to be colored.

Considering the electronic configurations, we see that only the Sc3+ ion does not have any unpaired electrons in its d orbitals. Therefore, the aqueous solution containing Sc3+ ions will be colorless.

Explanation:

1. Sc3+ ion:
- Sc3+ is the ion formed by the element scandium (Sc).
- The electronic configuration of Sc3+ is [Ar]3d04s0.
- Sc3+ does not have any unpaired electrons in its d orbitals, so it does not absorb any visible light.
- As a result, the aqueous solution containing Sc3+ ions will be colorless.

2. Fe2+ ion:
- Fe2+ is the ion formed by the element iron (Fe).
- The electronic configuration of Fe2+ is [Ar]3d64s0.
- Fe2+ has four unpaired electrons in its d orbitals, which can absorb certain wavelengths of visible light.
- Therefore, the aqueous solution containing Fe2+ ions will likely have a color.

3. Ti3+ ion:
- Ti3+ is the ion formed by the element titanium (Ti).
- The electronic configuration of Ti3+ is [Ar]3d14s0.
- Ti3+ has one unpaired electron in its d orbital, which can absorb certain wavelengths of visible light.
- Therefore, the aqueous solution containing Ti3+ ions will likely have a color.

4. Mn2+ ion:
- Mn2+ is the ion formed by the element manganese (Mn).
- The electronic configuration of Mn2+ is [Ar]3d54s0.
- Mn2+ has five unpaired electrons in its d orbitals, which can absorb certain wavelengths of visible light.
- Therefore, the aqueous solution containing Mn2+ ions will likely have a color.

Conclusion:
The aqueous solution containing Sc3+ ions will be colorless because Sc3+ does not have any unpaired electrons in its d orbitals.