Specifying Colors Using RGB and RGBA Formats
Prior to Max version 5, colors were specified as three integer numbers from 0-255 for the R, G, and B components. We call this the legacy or RGB color format. In Max 5, the new and preferred way to specify a color is with four floating-point numbers between 0 and 1. The first three numbers are for the R, G, and B components, and the fourth value is for alpha. We call this format RGBA. Alpha defines the transparency of the color. If the alpha is 0, you won't see the color at all. If the alpha is 1, the color is completely opaque. When converting between a legacy color style, the alpha is set to 1.
For compatibility with old patches, you can continue to send messages to objects to specify color in the legacy RGB format. However, in most cases, a new message has been defined for the RGBA format. For example, the comment object accepts a message frgb to set the text color using three integers (RGB format). It also accepts a new textcolor message to set the text color using four floats (RGBA format). In the Max Reference manual, RGB format messages are identified as Legacy RGB Format with a link to this page.