Modulex was a building system that was designed for adults. It was developed by The LEGO Group at the same time as their Architecture System of sets 750 Hobby and Model Box, 751 Hobby and Model Box, and 752 Hobby and Model Box. Modulex sets were produced from 1963 until 1965, These came in parts packs by color. The LEGO Group made Modulex a separate company in 1965, and the text "LEGO" was removed from the studs and replaced with "M". Modulex is not compatible with LEGO elements because the width to height ratio between the 2 brick types is different. LEGO bricks have a 6 to 5 width/length ratio, while Modulex has a cube type 5 to 5 width/length ratio
Modulex Brick Colors
Blue, Buff, Clear, Dark Blue, Dark Gray, Dark Green, Gray, Green, Lemon, Orange, Pastel Blue, Pastel Gray, Pastel Green, Pink, Red, Terra Cotta, Violet, Violet, White, and Yellow