Since I've had to look into it recently, I've got something minor to add.
Spoiler: Color modding: (click to see content)
For this, we'll be using Artmoney and/or Cheat Engine. They're not required (you could edit the memory by going to Debug/Memory Editor, going to VDP2 CRAM, and messing with values in there), but you'll find what you're looking for much faster with them (going down a large list of possibles at a time, versus going row by row, 8 possibles at a time).
The first thing you'll want is an address range to search within (for Artmoney, "Auto detect emulator by filename" should probably be turned off). These Action Replay cheats should help with that (Alt+L, click Action Replay, and add each of them):
VDP2 CRAM (5F00000-5F7FFFF)
15F00000 ABCD
15F7FFFE ABCD
First you'll do an exact value search at integer 2 bytes for ABCD (while emulation's paused). After that, clear the cheats list, and add them again, but with a value other than ABCD. Exact value filter for that new value, and that should get you 2 results, and a much better chance of finding what you're looking for (there doesn't seem to be a consistent color format all the games use, so I can't suggest a color value to search for).
Now, should you want to convert these to Action Replay codes, one thing you can do is to set the value of a bunch of addresses to 4148, and then go through the memory editor (Debug/Memory Editor, click Goto Address, and add 5F00000. Or click the right arrow until you see the VDP2 CRAM tab and click on it) to see if HAHA shows up in the ASCII column.
There's another way, but it involves using a hex calculator to subtract 5F00000 from the equivalent address you'd find in Artmoney/Cheat Engine, and then use the difference from that to offset the addresses of a copy/paste of your list of cheats. You'd then copy that list into notepad++, and get it to look like the above cheats (the 1's to specify the cheat is a 16-bit constant write) using the column mode select (hold Alt+Shift, press Up/Pageup/Down/Pagedown).
Also, you can use Debug VDP1 to get the x/y position to whatever sprites are listed. The values are displayed as decimal though.
If you're feeling lucky, you could even poke around the x/y position addresses and see if you can find anything to modify/rescale sprites (I've had to do this for 2 games because I couldn't color mod the black BG, and it's less codes you have to add).