Fibreglass is lovely but expensive

width is good, you may want to consider upsizing the length if you plan on doing laps.. a good kick-off & your almost half way across the pool before you've even started "swimming".
depth is good unless you want to jump or dive in. ( or have a slide)

Darker colour will help retain heat; ( good if you live northernly)... ( lighter is better if you live in a hot climate as it will reflect heat)