For example, green and yellow are colors of confusion in red-green CVD, but it is very common to mix forest green (█) with bright yellow (█). Mistakes by the colorblind increase drastically when uncommon shades are used, e.g. neon green (█) with dark yellow (█). For denotative tasks, using colors that are classically associated with a color name. For example, dont use burgundy (█) to represent "red". Unordered Information
A common task for designers is to select a subset of colors (qualitative colormap) that are as mutually differentiable as possible (salient). For example, player pieces in a board game should be as different as possible. Classic advice suggests using Brewer palettes, but several of these are not actually colorblind-accessible. A recent, free, powerful tool that checks color contrast of a group of colors is Adobes Color Blind Safe Tool. Unfortunately, the colors with the greatest contrast to the red-green colorblind tend to be colors of confusion to the blue-yellow colorblind, and vice versa. However, since red-green is much more prevalent than blue-yellow CVD, design should generally prioritize those users (Deutans, then Protans). Ordered Information
A common task for data visualization is to represent a color scale, or sequential colormap, often in the form of a heat map or choropleth. Several scales are designed with special consideration for the colorblind and are widespread in academia, including Cividis, Viridis and Parula (Matlab). These comprise a light-to-dark scale superimposed on a yellow-to-blue scale, making them monotonic and perceptually uniform to all forms of color vision.
Hallux rigidus or stiff big toe is degenerative arthritis and stiffness due to bone spurs that affects the metatarsophalangeal joints (MTP) at the base of the hallux (big toe). Hallux flexus was initially described by Davies-Colley  in 1887 as a plantar flexed posture of phalanx relative to the metatarsal head. About the same time, Cotterill first used the term hallux rigidus. Signs and symptoms
Pain and stiffness in the joint at the base of the big toe during use (walking, standing, bending, etc.) Difficulty with certain activities (running, squatting)
Swelling and inflammation around the jointAlthough the condition is degenerative, it can occur in patients who are relatively young, particularly active sports people who have at some time suffered trauma to the joint (turf toe). A notable example is NBA star Shaquille ONeal who returned to basketball after surgery. Causes
This condition, which occurs in adolescents and adults, can be associated with previous trauma. The true cause is not known. Most commonly, hallux rigidus is thought to be caused by wear and tear of the first metatarsophalangeal joint. Classification
In 1988, Hattrup and Johnson described the following radiographic classification system:

Grade I – mild changes with maintained joint space and minimal spurring. Grade II – moderate changes with narrowing of joint space, bony proliferation on the metatarsophalangeal head and phalanx and subchondral sclerosis or cyst. Grade III – severe changes with significant joint space narrowing, extensive bony proliferation and loose bodies or a dorsal ossicle.