差異基因表達熱圖上有紅色和綠色的"官方"標準用法嗎？

Although there is no standard as DeepTools' Devon Ryan said, there are still some habits. Usually red means upregulated, as you can see in the default color scheme in MATLAB's clustergram function. But you also want to make sure color-blinded people can see the difference. So another color scheme might be better, such as red=high while blue=low. Anyway, if you can easily flip the color, using red to represent high is expected.

In the absence of any yet-identified official recommendations, I will update this answer with resources as I find them:

Example usage in tutorials:

• EMBL Training: Red=Up, Black=NC, Green=Down

Program Defaults:

• PATRIC Webiste: Red=Up, Black=NC, Green=Down

Guides:

• Bio Turing Blog: Dos and don’ts for a heatmap color scale
• sebastianraschka: A short tutorial for decent heat maps in R

Tools (by year):

• (-2020) Web, R, CLI: MORPHEUS: Versatile matrix visualization and analysis software
• (2019) Web, R, CLI: NOJAH: NOt Just Another Heatmap for genome-wide cluster analysis
• (2017) Web, Jupyter: Clustergrammer, a web-based heatmap visualization and analysis tool for high-dimensional biological data
• (2017) Web, R: shinyheatmap: Ultra fast low memory heatmap web interface for big data genomics
• (2016) R: Complex heatmaps reveal patterns and correlations in multidimensional genomic data
• (2016) Web: Heatmapper: Web-Enabled Heat Mapping for All
• (<2016) GUI, Java, R: GENE-E
• (2015) R: Heatmap3: an improved heatmap package with more powerful and convenient features
• (2011) GUI, CLI: Gitools: Analysis and Visualisation of Genomic Data Using Interactive Heat-Maps

As others already pointed out, there is no official heatmap color scheme. I am not sure there is an official color scheme for any other types of plots either.

However, heatmaps seem to be far more standardized. Traditionally, heatmaps have been red-black-green as you originally stated. Most heatmaps from the microarray era and early RNA-seq are like that. You can have a heatmap for any type of data, but the majority is for gene expression. A lot of tools and tutorials were written back then, so they have that color scheme. From about 2008 to 2012, most people switched to the red-white-blue (or red-yellow-blue) color scheme. Switching green to blue avoids the color-blindness issue. Switching black to white is better for the ink if you print your papers and generally looks better on white background.

I originally found red as high to be confusing because I was thinking in financial terms (if the market is red, it's down). Now I think of it as a water faucet (red is hot, blue is cold).

Edit: In the last year or so, the viridis palette started to become widely used. It's far from the standard, but could become more popular in the future.