💬 Render equations in grey to support dark BGs (#12)

README.md

@@ -247,14 +247,14 @@ pass `"coarse"` as the second optional argument:
 ```
 
 Note that the equation in the NASA tutorial is incorrect. If 
-<img src="https://render.githubusercontent.com/render/math?math=\text{GCI}*">
-is the desired accuracy and <img src="https://render.githubusercontent.com/render/math?math=h*">
+<img src="https://render.githubusercontent.com/render/math?math=\color{grey}\text{GCI}*">
+is the desired accuracy and <img src="https://render.githubusercontent.com/render/math?math=\color{grey}h*">
 is the required resolution, then:
 
 <p align="center">
-<img src="https://render.githubusercontent.com/render/math?math=\displaystyle r = \left( \frac{\text{GCI}_{12}}{\text{GCI}*} \right)^{p^{-1}}">
+<img src="https://render.githubusercontent.com/render/math?math=\displaystyle\color{grey} r = \left( \frac{\text{GCI}_{12}}{\text{GCI}*} \right)^{p^{-1}}">
 </br></br>
-<img src="https://render.githubusercontent.com/render/math?math=\displaystyle h* = \frac{h_1}{r}">
+<img src="https://render.githubusercontent.com/render/math?math=\displaystyle\color{grey} h* = \frac{h_1}{r}">
 </p>
 
 ## License