False-color wavelength assignments in this "drop-dead gorgeous" image of NGC 2903?
Spacetelescope.org
indicates under "Colours &amp; filters" that the blue channel of the image is from a 658 nm filter (red)
and the red channel is from an 814 nm filter (near infrared).
The cyan and orange rows of the table also list these filters; presumably the green channel is a blend of the two.

The ACS instrument handbook says filter F658N is narrow, passing only NII or slightly redshifted H&alpha; emission (Table 5.1, Figure 5.4).
Filter F814W is wide, passing wavelengths between 710 nm and 960 nm (Table 5.2, Figure 5.1).

NGC 2903 is one of the brighter galaxies not in the Messier catalog.
Here is a wider angle, more natural RGB image by Bob Franke, rotated for easier comparison.
The reddish emission nebulae here appear blue in the HST image.