New Post: Multivariate symbology

Yes this is possible using a FeatureScheme with unique values.

PointScheme myScheme = new PointScheme();
myScheme.EditorSettings.ClassificationType = ClassificationType.UniqueValues;

You have to add one category for each combination you need and set the filterExpression to the values that result in the shown symbol. In the example below you'd have to change the color and size values to create the other categories you need.

PointCategory largeSize = new PointCategory(Color.Yellow, DotSpatial.Symbology.PointShape.Star, 16);
largeSize.FilterExpression = "[Size] = '16' AND [Color] = 'Yellow' ";
myScheme.AddCategory(largeSize);