In GIS, in addition to the color matching of the base map, the display effect of different elements on the base map is often considered.
Some features have accepted color schemes, such as precipitation, radar, and so on.
The image above is from the National Weather Information Center
However, there are no standards for most elements, and the color matching of each weather platform is also different.
Color matching principle
The color matching principle of the color spot map is to divide various weather elements (such as precipitation, temperature, etc.) into different colors according to a certain magnitude, so as to facilitate the grasp of the overall regional weather changes. In practical application, attention should be paid to the meaning represented by the color scale.
The picture above is from Hangzhou Meteorological Network
color scheme
Segmented color matching
There is only one color in the area between one node and another node, what we need to set is the color of each area. This color matching method is generally used on elements that need to be graded, such as precipitation, wind level, air quality, etc.
gradient color
Set a value on a node, and the gradual transition between nodes will be automatically performed. What we need to set is the value of each node.
In professional weather services, we often use segmented color matching. In public weather services, gradient colors are more common. This is because professional users have higher requirements for data accuracy, and it is necessary to ensure that users can quickly judge the grade interval of elements on maps of different scales. When facing public users, gradient color matching can make the data look smoother and more visually beautiful. 
Therefore, the radar map of the Central Meteorological Station is segmented (left), while the radar map of Caiyun Weather is gradual (right).
Add gradient color matching in the segment
In addition to gradient color matching and segmented color matching, they can also be mixed into a unique color matching method.
The picture above is from GRlevelX
For example, in GRLevelX, on the basis of segmented color matching, gradient color matching is superimposed in each segment, so the display effect is more three-dimensional. The color inside the segments is smoother.
Problems in Color Scale Axis Color Matching
Can colors in different intervals be similar?
The picture above is from the official media of the National Weather Service Weather Forecast Center
On a map released by the Weather Prediction Center of the National Weather Service, the color scale axis of the temperature anomaly is between 22 ~ 35 and -22 ~ -35, 35 ~ 50 and -35 ~ -50, and 0 ~ 6 The colors are very similar.
According to the law of numerical values, we can know that in the same area, it is impossible to have high and low values at the same time at two very close grid points, and there must be other numerical values among them. Therefore, similar colors that are far apart will not cause display confusion. In the case of a large value span and fine color grading, similar colors can appear in high and low values.
When do you need a transparent color scale?
Clouds, radar, wind, precipitation, etc., the values of these elements have one thing in common, that is, the minimum value is 0. Often we do not need to focus on this element when the value is 0 or below a certain value. So at this time, the color of their minimum value or minimum segment can be set to be transparent, that is, the color of the feature will not be displayed when the value is lower than a certain value on the map.
How to ensure that text or lines can be seen clearly in all colors on the color spot map?
Sometimes it is necessary to superimpose text on the color spot map, such as place names, element values, etc., but after the color spots are superimposed, if the color of the text is similar to the color of the color spots, the display will not be clear. At this point we have two optimization methods:
Method 1
Add styles such as strokes, shadows, or background colors to the text. The
above pictures are from Caiyun Weather , Windy , and the National Meteorological Information Center.
Method 2
: Set the text to automatically change color following the background color, text on a dark background is displayed in white, and text on a light background is displayed in black.
The image above is from Highpoint Weather
Some reference articles:
How to choose color matching - Help Center - MapHui
Product Color Matching 2.0: Use HCL color space instead of HSL to generate color matching
Color matching tool recommendation:
Colorpicker for data