Hello! I've noticed that Mecabricks tries to stay close to LEGO's color catalog where possible, which I think is wonderful.

However, I have noticed there are some descrepancies in the color catalog available in the program, so I figured I'd share them here. I'll reference Bricklink's colors a lot, as they are the best point of reference when it comes to color usage in sets. Hopefully this is comprehensible xd

221 Bright Purple & 22 Medium Reddish Violet :
The current color titled Medium Reddish Violet appears to me to be intended to be the Bricklink's 'Medium Dark Pink'. The correct color for this is 16 Pink. Meanwhile, the color known as 22 Medium Reddish Violet is, much like 221 Bright Purple, known on Bricklink as 'Dark Pink'. The two colors are very similar and hard to distinguish, however in general, Dark Pink parts from before 2004 were Medium Reddish Violet; the change-over to Bright Purple occured co-currently with the other color changes of 2004.

19 Light Brown:
Based on the general color given to this in the program, I assume it's meant to be Bricklink's 'Fabuland Brown'. The correct LEGO equivalent here would be 4 Brick Red. 19 Light Brown is Bricklink's 'Fabuland Orange'.

216 Rust:
Oh boy, this is a big cookie.
Bricklink's Rust color refers to an off-colored variation of 21 Bright Red, as well as 13 Red Orange (known in some parts of the community as Fabuland Red, used most notably for a duplo cow and Marc Monkey from Fabuland). The color 216 Rust more so resembles 38 Dark Orange, as listed as on Bricklink in sets 7921 and 5962.

150 Metallic White Grey:
I've never heard this color being named Metallic White Grey, just 'Light Grey Metallic' or 'Metallic Light Grey' (the latter as of 2003-ish, same pattern can be applied to most early metallic colors)

316 Titanium Metallic:
Not really an issue here, but just figured I should note, similar to the Dark Pink BL situation, pre-2010 'Pearl Dark Grey' is 148 Dark Grey Metallic/Metallic Dark Grey, and post-2010 is 316 Titanium Metallic.
Additional note: Co-current with this was the change over from 131/301 Silver to 315 Silver Metallic. Contrary to BL's Flat Silver/Pearl Light Grey split, there was only one main silver color active for most of pre-2010 (with an exception in 2006). Like most early metallic colors however, the appearance of 131 Silver varies heavily between material, which is what has lead to Flat Silver/Pearl Light Grey.

Metal/Ink:
Currently, the Metal colors are referred to as 2004 Silver Ink, 299 Gold Ink, and 334 Copper Ink. So first thing I want to note here, the IDs of the first two:
335 Gold Ink and 336 Silver Ink, would be the more correct IDs. Secondly, the Ink colors appear to be in reference of both 'Metal' colors and Chrome colors, this is to mean 336 Silver Ink incapsulate both 309 Metalized Silver and 298 Cool Silver, Drum Lacquered, the latter referring more specifically to the 'Metal' silver. The other two metal colors here would be 300 Copper, Drum Lacquered and 299 Warm Gold, Drum Lacquered.

200 Lemon Metallic:
This is a pearlescent color that was used pretty much exclusively for the Krana-Kal of BIONICLE Lehvak-Kal, and several BIONICLE Kraata. As far as we know, metallic colors did not have names at the time, but LEGO has referred to the metallic coating seen in sets 8465 and 8466. The part names however reveal the name of "GR.METAL"; "LACQ. PANEL NO. 3 (GR.METAL)" - though I'd take that name with a grain of salt.

The Chromes:
I'm not sure what 2000 Metallic Earth Orange is supposed to be, but I'd presume Antique Gold (Bricklink's 'Chrome Antique Brass'). 187 Metallic Earth Orange is the pearl brown color used for Rahkshi Panrahk, and the same cases can be applied to 185 Metallic Bright Blue and 186 Metallic Dark Green. I'm unsure the older chrome colors like the green, pink, and blue, would have names or IDs. (As far as we know, the silver and gold only got IDs around 2012 I believe?)
Additional note here is that the chrome colors in general do not appear to be one color in themselves - for example, there's the chrome blue part 4143278 / 23292 "PRINCESS CROWN METAL COL. 102", 102 being Medium Blue. Make of that what you will.

As a final note, sadly 153 Tr. Fluor. Blue is discontinued as of 2018-ish, and it's looking like 47 Transparent Fluorescent Reddish Orange is in its final year.
346 Copper Metallic also appears discontinued as of this year. It seems LEGO has implimented a new system of temporary colors, which this color, as well as Vibrant Coral, the Opal colors, and glitter Tr. Br. Green/Orange are under, which lets them be around for a run of 4 years. Perhaps as a trial period? I don't know. Bright Bluish Green is not part of this system though, it seems it's here to stay.