I just got home and finally can actually use my computer to post here.
Firstly, a couple of days ago I got the 'brilliant' idea to bulldoze all of the houses and houseboats (except for one) from Isla Paradiso. My reasoning is there are so many bad builds in that world and none of them were fixed by the world that EllaCharmed fixed (as far as I know). I think the only thing she did was something I can't do - take it into Create a World and fix all the problems caused by problems with the world itself - such as badly placed rocks and trees and roads not joined up correctly.
Since I've been looking for worlds with no sims and no houses in them to use as part of my McFluff story I decided to get the fixed version of Isla Paradiso and bulldoze everything I could. I had to leave one houseboat as that's where my one and only sim is living. The only Sims I kept in the world are the 4 mermaids - Maya Ocean, Mia Azul, Triton King and Salty Seaworth.
I haven't had a chance to try it out yet in a game but it is a save that I plan to use when I do get around to it.
I've discovered that it seems to be only the mermaids from Isla Paradiso that are generated with bare legs and no scales or tail.
I have done quite a lot of work with mermaids over the past few months and I've added dive lots to several worlds including Sunlit Tides, and several player made worlds. In each case, when I added a dive lot I'd made myself, mermaids were generated by the game and they all had their tails. Their tails were always the generic purple for females and blue for males, but the did always have them.
For example, this mermaid turned up in a dive lot I made for Cake Island. She is wearing the default purple tail the game gives to female mermaids.
https://s5.postimg.cc/xptydj1uv/BriannaOlivares001.jpg
I'd have to dig for screenshots of others but I got at least 2 different mermaids with tails in Sunlit Tides. So it seems to me it is only the mermaids from Isla Paradiso that are affected.
The other thing I discovered is it is only seems to be from new games. For example, I found an old game from several years ago and in that game my household hadn't been diving and had no contact with any of the 4 mermaids from Isla Paradiso. When they went diving those mermaids all eventually appeared in their original tail colours. They are the mermaids I used to read the correct colours from. I noticed the numbers vary slightly if the mermaids are taken into Stylist with their tails on. I think the numbers must be some sort of an average and are slightly different between tails and scales. If they are taken into wherever they go when you use the mirror for them to change their scale colour the numbers are a little different.
I discovered I can't change the scale colours in CAS or Stylist. I can only do it via the mirror.
But if you have Master Controller, and they are swimming with their tails on you can take them into Stylist with their tails on and it is a special outfit. But be careful that you don't accidentally change their everyday outfit to their tail or you'll have a mermaid walking around with their tail on and it looks like they are wearing a sack.
I've also discovered toddler mermaids have yellow/orange scales/tails if they are male and pink scales/tails if they are female. You can use the mirror to change their colours to whatever you like. I've been having fun experimenting with different scale/tail colours.
I've been making my own mermaids and playing with scale/tail colours.
https://s5.postimg.cc/ablz1j71z/MermaidsUW012.jpg
You'll see the 4 from Isla Paradiso here too.
https://s5.postimg.cc/fn0vmbt5j/MermaidsUW004.jpg
You can see Triton King with the blue default scale colour the game gives male mermaids when the Mermaid Occult is added to them.
https://s5.postimg.cc/3ubh5muk7/CI_DL005.jpg
This is Triton King with his original tail colour.
https://s5.postimg.cc/px3alk3lj/MermaidsUW007.jpg
And when I took him into Stylist using Master Controller
https://s5.postimg.cc/djqgeze0n/TritonKingInStylist002.jpg
It is possible to change the scale colours in stylist but they are wearing their tail and I found the numbers are a bit different sometimes in stylist than when they use the mirror to change their leg scales.
Now, I can give you the numbers for the 4 mermaid scales that I found when I checked the colours of the original Triton King, Mia Azul, Salty Seaworth and Maya Ocean.
Triton and Mia are both Adults while Salty and Maya are Young Adults.
I found you have to have the mermaid under your control and they have to already have the Mermaid Occult assigned to them and have their leg scales when out of the water before you can get them to go to a mirror to Change Scale Color.
Take them to a mirror and choose Change Scale Color (I've noticed not all mirrors will have this option so if your mirror doesn't have it try another mirror).
I got the colour numbers from them when they are wearing their leg scales, not their tails. The numbers are slightly different if they have their tails.
I got the numbers by opening an old game from a few years ago that I found on an old backup external drive. That game had the four mermaids and they all had their original scale colours. @lanlyn also has a set of numbers that she found somewhere and some of them are not exactly the same as mine. But they do look very close to the appearance of my mermaids so I'll give you the scale colours I got from my mermaids.
Here are the original scale colours I have obtained from the four Isla Paradiso mermaids. The numbers below will give you these scale colours for each mermaid when you click on a mirror and choose Change Scale Colour.
https://s5.postimg.cc/jqwm1syxz/Original_Scale_Colours001.jpg
When you get into Change Scale Colors you will see a colour wheel on the upper left of the screen. Click the make the colour wheel visible. It will not be on top when you first open it.
The panel on the left is what you will see first. Click on the tab to show the panel with the colour wheel and the place to enter the R G B numbers.
https://s5.postimg.cc/vhajj89qv/Default_Female_Scale_Colours001.jpg
https://s5.postimg.cc/hnm6u6ovb/Default_Male_Scale_Colours001.jpg
I used Triton King as the example. On the left you see him with the default male mermaid scale colours. This is the colour that all male mermaid tails are by default. The exception is toddlers - male toddlers get yellow/orange scales and female toddlers get pink scales.
Then at the top of this panel click on the topmost coloured circle. It is Yellow in the Triton King diagram below but will be some other colour if you are using it to change your mermaid scales from the defaults.
https://s5.postimg.cc/ya3r3as3r/Triton_King_Diagram001.jpg
I've given you the R G B numbers to use. Each is in a column that corresponds to the colours at the top of the panel. Left to right columns below correspond with top to bottom colours in the panel.
Mia Azul
R 170 - 0 - 1 - 170
G 196 - 200 - 159 - 196
B 229 - 207 - 110 - 229
Maya Ocean
R 159 - 104 - 104 - 104
G 222 - 153 - 153 - 153
B 203 - 211 - 211 - 211
Salty Seaworth
R 100 - 61 - 68 - 167
G 109 - 62 - 105 - 161
B 116 - 167 - 151 - 150
Triton King
R 240 - 240 - 69 - 70
G 196 - 240 - 100 - 222
B 97 - 240 - 151 - 240
I'll make a video to show this more clearly too. When it's done I'll post a link here.