UJML provides several different ways to determine the device context for colors. See UJML Colors.

Not all devices provide color displays. You can determine device support for color by calling the _getBooleanProperty() function with the &_PROPERTY_BOOLEAN_COLOR_CAPABLE; device information entity. See _getBooleanProperty() function, Boolean Device Information Entities. Devices without color support usually convert colors to a similar, gray-scale, value.

Not all devices provide the same number of colors, or of gray-scale levels if they do not support color. You can determine the device color depth/number of gray-scale levels using the _getIntProperty() function with the &_PROPERTY_INT_COLOR_DEPTH; device information entity. See _getIntProperty() function, Integer Device Information Entities.

Not all devices support alpha opacity in colors or images. You can determine device support for alpha opacity by calling the _isSupported() function with the &_COLOR_ALPHA; device information entity. See _isSupported() function, Feature Support Information Entities.

UJML Colors, _getBooleanProperty(), Boolean Device Information Entities, _getIntProperty(), Integer Device Information Entities, _isSupported(), Feature Support Information Entities