Generally the majority of low level graphics code is written in C++, sometimes with smatterings of assembly to take advantage of SIMD hardware (or more likely nowadays compiler intrinsics which allow access to specialized processor features through C++ function calls and types). Increasingly I spend a lot of my time working with various shader languages that target GPU hardware.

Many games nowadays also use a higher level scripting language for gameplay (rather than engine) code. As a graphics programmer I usually spend less time working at that level than a gameplay programmer would but I usually end up dealing with some UnrealScript, lua or whatever the current project is using for scripting.

Although my focus is on the runtime side I also work on graphics related tools and pipelines on occasion (level editors, model viewers, data compression, data build pipelines, etc.). The technologies used vary but I've done a fair bit of C# and Python coding plus bits of things like MaxScript and javascript (for scripting Photoshop).