Because the flash light is a lot "bluer" than tungsten light. In order to balance the warm glow of tungsten, the camera will add blue (this is the Reader's Digest version) to make colors appear normal. When you added the bluer light of the flash to a tungsten balanced shot, the cat got very blue..
What you can do about it is, don't do that. Use Flash WB for flash shots, tungsten balance for tungsten shots, sunlight balance for sunnshiny shots etc. Otherwise you will create many problems..
You would be better off to set the camera to Auto WB until you understand what you are doing..
Nothing is enough for the man to whom nothing is enough...
When you set the WB for tungsten/incandescent, the camera is trying to compensate for the warmer color of the incandescent light by adding more of a blue bias to the picture. You should have better luck using one of the WB for flash..
Have you never noticed that daylight, (and flash light too) are both blue by comparison with domestic tungsten lighting? Or rather, since it was daylight that was around first(!) it is domestic tungsten lighting that is very yellow by comparison? This is particularly noticeable at dusk, when artificial lights are first switched on..
You may also notice that many fluorescent lights tend to be greenish..
Your digital camera has white balance presets for all these different kinds of "white" and probably also has a custom mode (Custom WB) for producing a workable balance for any oddball lighting without an onboard preset..
Note: Flash can still be used when mixed with tungsten lighting, but to get rid of the blue you need to cancel it with a special coloured gel filter. A light orange one is needed (CTO). Or you could use light green to match to fluorescent, and then use a fluorescent WB setting to shoot..
Swatch books of masses of multi-purpose coloured gels, made just big enough to cover a flash, are available pretty much for free, by approaching LEE FILTERS agents, or the ROSCO INTERNATIONAL company..
Because 'blue flash' matches 'daylight blue' quite closely, you do not need to filter anything when using flash mixed with daylight (often called 'synchro-sun').Regards,Baz..
Use whatever light source you want, and set your cameras WB to match it. And don't mix the light types...if it is daytime, and you are shooting the cats with interior tungston lights (and your cam is set for tungston WB), shut the shades so the daylight won't negatively affect your tungston WB setting... OR, turn off the lights, open the shades, reset your cameras WB setting to daylight, and shoot away. Good Luck..
When you shoot with flash and camera set to tungsten it is the same thing you get with a film camera shooting tungsten film in daylight.http://vette74.smugmug.com..