Powder Toy has several modes for displaying the wealth of information contained in every frame. At the moment, the chief way to access them is using the numbers on the keyboard, 1 through 9 and 0.
If you want, you can also use the rainbow-colored button next to the login box to change display modes, but this is a custom UI and can use effects not covered here.
Velocity display shows wind speeds and positive pressure. Blue is up/down, red is left/right. Any combination of the colors is a combination of direction, so that diagonal wind lines are magenta.
Positive pressure is shown as green, which is essentially air that isn't moving.
In velocity view, negative pressure is not rendered.
Pressure display shows the pressure value of the grid. Red is high pressure (can be created w/ AIR) and blue is low (can be created w/ VAC).
Persistent display sustains elements' traces for a few seconds after they have left the location. It is useful to track motions, and also makes for a very nice effect on some saves (Spinning GRAV Colors is a good example). Essentially Motion Blur mode.
"Normal" display. Displays most effects, and includes heat-sensitive metal color changing. Does not include "fancy" effects such as fluid blurring, extensive glows, etc.
Makes everything blobby.
Heat displays different colors for different temperatures, like a thermal camera.
Fancy displays different effects for elements. For example, Plutonium and uranium glow, and water has a more fluid-like appearance (both shown below) Photons also receive a glow effect and steam appears as a gray cloud with a purple lining. Introduced "fancy lensing" for Newtonian gravity (v53.1 beta). This "fancy" effect demonstrates how the path of light can be bent by dense masses (WHOL, BHOL and GPMP), the effect is most perceptively visual with GPMP, the light is so warped it creates an "event horizon" where nothing can escape.
Nothing display only displays the element's true color - no effects at all are shown.
Renders particles with brighter or darker variations of their default color depending on their temperature, in such a way that heat diffusing through substances produces obvious waves.
Renders X and Y velocity as white, but displays positive and negative pressure as red and blue just like pressure display.
Displays current life values of all particles in greyscale gradients. Similar to the waves in heat gradient view.
To get to it, you need to be in debug mode 'd' , You can then cycle through the displays to get to it. Its shortcut is shift-1 (only works in debug obviously).
Pressing "g" in-game will activate the grid function. There are nine grids varying in size.