How-to align ListPlot with ArrayPlot and Label some Points

Question

I would like to overlay ListPlot on ArrayPlot. I have explored a number of posts, but I did not manage to achieve the desired outcome. Hence, the reason for the post. Following is a visual representation of what I want to achieve.

1. Set custom axes;
2. Align ArrayPlot to ListPlot axes;
3. Plot points with labels;

Here is the grid I would like to overlay...

colors = RGBColor /@ {"#c7e8ac","#ffeca9","#ff8f80"}

grid = {
{Yellow,Yellow, Red, Red, Red},
{Green, Yellow, Yellow, Red, Red},
{Green, Yellow, Yellow, Yellow, Red},
{Green, Green, Yellow, Yellow, Yellow},
{Green, Green, Green, Green, Yellow}
} /.{
Green-> colors[[1]]
, Yellow-> colors[[2]]
, Red-> colors[[3]]
};

ArrayPlot[
 grid
 , Mesh -> True
 , Axes -> True
]

and the data would be generated in the following way...

Outer[{#2, #1, #1*#2} &, Range[0.01, 1, .01], Subdivide[1000, 20000000, 1000]] // Flatten[#, 1] &;

I have tried to implement a solution using Epilog and Inset. However, the results are suboptimal...

The code used for the above...

ListPlot[
 {{5000, 0.05}}
 , PlotRange -> {{0, 10^6}, {0, 1}}
 Epilog -> Inset[
   ArrayPlot[
    grid
    , Mesh -> True
    ]
   , Scaled[{0.02, 0.02}]
   , Scaled[{0, 0}]
   , Scaled[1]
   ]
 ]

Answer 1

(1) Use the option AspectRatio -> 1 in ListPlot[...], (2) use Prolog (instead of Epilog) so that the points and lines are not covered by inset object, (3) add the options PlotRangePadding -> None and ImagePadding -> None to ArrayPlot:

lp = ListPlot[{{{50000, 0.05}}, {{500000, 0.7}}}, 
  PlotLabels -> {"Label 1", "Label 2"}, 
  PlotStyle -> Directive[Black, PointSize[Large]], 
  PlotRange -> {{0, 10^6}, {0, 1}}, 
  Prolog -> 
   Inset[ArrayPlot[grid, Mesh -> True,
           PlotRangePadding -> None, ImagePadding -> None], 
    Scaled[{0, 0}], Scaled[{0, 0}], Scaled[1]], AspectRatio -> 1]

Post-process to change the styling of callout lines:

lp /. {Directive[AbsoluteThickness[4], ___], ___} :> {} /. 
 b_BSplineCurve :> {Black, b}