Both organic and inorganic by filtering through an accurately re-dried filter paper, which can be GFC or GCA, depending on size of particles they will filter. Filter a known amount using a vacuum pump, need a litre for very clean water. Dry in an oven at 104oC for at least 2 hours, allow to cool and weigh. Can also measure settleable solids, use a known amount of effluent in an Imhoff cone and measure rate of settling in a set rate of time. Also shows if you've got humic acids.
True colour is dissolved colloids apparent is due to solids.
Some effluents can be amazing colours like at Cramlington. Compare against standards, results expressed as Hazen units. It's important as it indicates buffering capacity of water, affects chemical treatment, water softening, corrosion, problems of acidification and high alkalinity in rivers and streams will affect aquatic life. All acids contain hydrogen , all alkalines contain OH group. Use pH meter, titration to determine total acidity and total alkalinity or can use pH indicator papers.