here is how i do my pinks. i'm sure it's not the only way but i've had years of successful results. first layer is n3 flux on silver. that's usually my basecoat for holding my wirework. next coat under any pink i will use is ninomaya H13. name may have changed to N13, not sure as they've undergone some number changing. then i use my other pinks. i can fire these as many times as i like without color change. think about the principles involved and the factors which you can control.  what is making the pink turn to orange? two things: proximity to the fine silver base causing a chemical reaction, and exposure to a higher temperature. so....add buffer layers of enamel under the pink. i've also used light blues, grey, etc. colors which don't significantly change the hue of the pink i'm using but add an extra layer of protection. and then, don't overfire. what is overfired? when the time/temperature relationship is great enough (a combination of too hot and too long firing time) to create a result you don't want! so play around with those two factors. be a scientist and systematically test different factors on very simple little tests. fyi, i also use n3 flux as my cover layers on all of my cloisonne.