Tonality of colour (lightness or darkness of a colour) and tonal contrast (between colours) is a more important consideration in dementia-specific design than the selected colours themselves. Tonal contrast attains significance in the design due to the reduced cognition and visual abilities of residents, and where the available light (natural or artificial) is too bright, minimal or fluctuates over periods of time. Difficulties in identifying interior elements may place residents at risk and reduce their level of independence.
The specification of inappropriate lighting can cause both disability and discomfort glare. Safe and comfortable visual environment depends on a number of factors: avoidance of excessive illuminance variations; absence of direct glare from lamps, luminaires or windows; appropriate luminance distribution on interior surfaces; use of suitable colours on the main interior surfaces; use of light sources with suitable colour characteristics Rarely, if ever, are all of the preceding points achieved together in mainstream design, let alone in aged care accommodation. There is still no Standard otherwise, which specifically addresses Lighting in Aged Care in general or in Dementia-specific accommodation.
Colour contrast strategies assume standard colour vision and perception, and are dependent on appropriate lighting. Tonal contrast strategies recognise diminished visual ability and are far less dependent on the prevailing light conditions. Good sense suggests that tonal contrast strategies should be addressed at the commencement of the design process to ensure that cueing and wayfinding strategies are embedded in the design.