Unfortunately neither colour nor turbidity are strong indicators of the overall chemical composition of water. However both colour and turbidity reduce the amount of light penetrating the water and can have significant impact on algae and macrophytes.
Wines range from 0 to about 220 grams per liter sugar, depending on the style. Dry wines can contain up to about 10 grams of sugar per bottle but still taste dry. Bone Dry <1 cal per glass. Dry 0-6 cal per glass.
Add the corn sugar to the wine about 1 pound at a time, stirring between each addition to dissolve the sugar. Measure your sugar level of the juice (juice only, no pulp), being careful not to go above 1.085. You may need more or less sugar than the recipe calls for based on the ripeness of your grapes.