# Generating functions and plotting them with different colors

Let's say I have the logistic function

```
f(x) = a / (1 + b*e^(-(x-c)/d))
```

For `a`

, the value will likely not change, it stays fixed at 1. `b`

will remain in the meanwhile at `0.2`

, but I would like to plot all other variants of the function for x in the interval `0, 21`

for different values of `c`

and `d`

in different colors (like color lerp).

Like, for all combinations of `c,d`

in `[0.2,0.4,0.6,0.8,1.0,1.2]`

How to achieve this in sage 5.2 and python? I've tried simply using a python function that returns a "sage function" but it doesn't work.